Feature/save signs (#2127)

* apply fix

* Fixes empty th:action

* Update build.gradle

* fix

* formatting

* Save signatures

* Fix code scanning alert no. 42: Uncontrolled data used in path expression

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* fix UserServiceInterface

* Merge branch 'feature/saveSigns' of
git@github.com:Stirling-Tools/Stirling-PDF.git into feature/saveSigns

* 0.31.0 bump and further csrf

* formatting

* preview name

* add

* sign doc

* Update translation files (#2128)

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---------

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Co-authored-by: Dimitrios Kaitantzidis <james_k23@hotmail.gr>
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src/main/java/stirling/software/SPDF/model/SignatureFile.java

@@ -0,0 +1,11 @@
+package stirling.software.SPDF.model;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+
+@Data
+@AllArgsConstructor
+public class SignatureFile {
+    private String fileName;
+    private String category; // "Personal" or "Shared"
+}