SSO Refactoring (#2818)

# Description of Changes

* Refactoring of SSO code around OAuth & SAML 2
* Enabling auto-login with SAML 2 via the new `SSOAutoLogin` property
* Correcting typos & general cleanup

---

## Checklist

### General

- [x] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [x] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md)
(if applicable)
- [x] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md)
(if applicable)
- [x] I have performed a self-review of my own code
- [x] My changes generate no new warnings

### Documentation

- [x] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [x] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [x] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/DeveloperGuide.md#6-testing)
for more details.

src/main/java/stirling/software/SPDF/model/ApplicationProperties.java

@@ -1,5 +1,7 @@
 package stirling.software.SPDF.model;
 
+import static stirling.software.SPDF.utils.validation.Validator.*;
+
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -12,7 +14,6 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
-import java.util.stream.Collectors;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.context.annotation.Bean;
@@ -34,10 +35,11 @@ import lombok.extern.slf4j.Slf4j;
 
 import stirling.software.SPDF.config.InstallationPathConfig;
 import stirling.software.SPDF.config.YamlPropertySourceFactory;
-import stirling.software.SPDF.model.provider.GithubProvider;
+import stirling.software.SPDF.model.exception.UnsupportedProviderException;
+import stirling.software.SPDF.model.provider.GitHubProvider;
 import stirling.software.SPDF.model.provider.GoogleProvider;
 import stirling.software.SPDF.model.provider.KeycloakProvider;
-import stirling.software.SPDF.model.provider.UnsupportedProviderException;
+import stirling.software.SPDF.model.provider.Provider;
 
 @Configuration
 @ConfigurationProperties(prefix = "")
@@ -136,13 +138,13 @@ public class ApplicationProperties {
                     || loginMethod.equalsIgnoreCase(LoginMethods.ALL.toString()));
         }
 
-        public boolean isOauth2Activ() {
+        public boolean isOauth2Active() {
             return (oauth2 != null
                     && oauth2.getEnabled()
                     && !loginMethod.equalsIgnoreCase(LoginMethods.NORMAL.toString()));
         }
 
-        public boolean isSaml2Activ() {
+        public boolean isSaml2Active() {
             return (saml2 != null
                     && saml2.getEnabled()
                     && !loginMethod.equalsIgnoreCase(LoginMethods.NORMAL.toString()));
@@ -158,6 +160,7 @@ public class ApplicationProperties {
         @Setter
         @ToString
         public static class SAML2 {
+            private String provider;
             private Boolean enabled = false;
             private Boolean autoCreateUser = false;
             private Boolean blockRegistration = false;
@@ -195,7 +198,7 @@ public class ApplicationProperties {
                 }
             }
 
-            public Resource getidpCert() {
+            public Resource getIdpCert() {
                 if (idpCert == null) return null;
                 if (idpCert.startsWith("classpath:")) {
                     return new ClassPathResource(idpCert.substring("classpath:".length()));
@@ -225,12 +228,11 @@ public class ApplicationProperties {
             private Collection<String> scopes = new ArrayList<>();
             private String provider;
             private Client client = new Client();
+            private String logoutUrl;
 
             public void setScopes(String scopes) {
                 List<String> scopesList =
-                        Arrays.stream(scopes.split(","))
-                                .map(String::trim)
-                                .collect(Collectors.toList());
+                        Arrays.stream(scopes.split(",")).map(String::trim).toList();
                 this.scopes.addAll(scopesList);
             }
 
@@ -243,32 +245,31 @@ public class ApplicationProperties {
             }
 
             public boolean isSettingsValid() {
-                return isValid(this.getIssuer(), "issuer")
-                        && isValid(this.getClientId(), "clientId")
-                        && isValid(this.getClientSecret(), "clientSecret")
-                        && isValid(this.getScopes(), "scopes")
-                        && isValid(this.getUseAsUsername(), "useAsUsername");
+                return !isStringEmpty(this.getIssuer())
+                        && !isStringEmpty(this.getClientId())
+                        && !isStringEmpty(this.getClientSecret())
+                        && !isCollectionEmpty(this.getScopes())
+                        && !isStringEmpty(this.getUseAsUsername());
             }
 
             @Data
             public static class Client {
                 private GoogleProvider google = new GoogleProvider();
-                private GithubProvider github = new GithubProvider();
+                private GitHubProvider github = new GitHubProvider();
                 private KeycloakProvider keycloak = new KeycloakProvider();
 
                 public Provider get(String registrationId) throws UnsupportedProviderException {
-                    switch (registrationId.toLowerCase()) {
-                        case "google":
-                            return getGoogle();
-                        case "github":
-                            return getGithub();
-                        case "keycloak":
-                            return getKeycloak();
-                        default:
-                            throw new UnsupportedProviderException(
-                                    "Logout from the provider is not supported? Report it at"
-                                            + " https://github.com/Stirling-Tools/Stirling-PDF/issues");
-                    }
+                    return switch (registrationId.toLowerCase()) {
+                        case "google" -> getGoogle();
+                        case "github" -> getGithub();
+                        case "keycloak" -> getKeycloak();
+                        default ->
+                                throw new UnsupportedProviderException(
+                                        "Logout from the provider "
+                                                + registrationId
+                                                + " is not supported. "
+                                                + "Report it at https://github.com/Stirling-Tools/Stirling-PDF/issues");
+                    };
                 }
             }
         }
@@ -335,10 +336,10 @@ public class ApplicationProperties {
         @Override
         public String toString() {
             return """
-            Driver {
-              driverName='%s'
-            }
-            """
+                    Driver {
+                      driverName='%s'
+                    }
+                    """
                     .formatted(driverName);
         }
     }