Implement user management enhancements and password change functionality

- Add change password feature in UserService, allowing users to update their password after verifying the current one.
- Introduce UpdateUserRequest model for updating user details, including username, password, and role.
- Implement RESTful endpoints for changing passwords and updating user information in AuthResource and UsersResource.
- Enhance OpenAPI specification to document new endpoints for password change and user updates.
- Create frontend components for user management, including a dedicated UsersPage for admin users to manage user accounts.
- Add unit tests for UserService to ensure correct behavior of password changes and user updates.

src/main/resources/openapi-roleplay-public-v1.yml

@@ -445,6 +445,31 @@ paths:
         "401":
           description: Not authenticated.
 
+  /auth/change-password:
+    post:
+      operationId: changePassword
+      summary: Change password
+      description: Changes the current user's password. Requires current password verification.
+      tags:
+        - auth
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/ChangePasswordRequest'
+      responses:
+        "204":
+          description: Password changed.
+        "400":
+          description: Current password wrong or validation failed.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorResponse'
+        "401":
+          description: Not authenticated.
+
   /admin/users:
     get:
       operationId: listUsers
@@ -493,6 +518,72 @@ paths:
         "403":
           description: Forbidden (admin only).
 
+  /admin/users/{userId}:
+    put:
+      operationId: updateUser
+      summary: Update user (admin only)
+      description: Updates an existing user by id. Username and role required; password optional (omit to keep current).
+      tags:
+        - users
+      parameters:
+        - $ref: '#/components/parameters/UserId'
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/UpdateUserRequest'
+      responses:
+        "200":
+          description: User updated.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/UserSummary'
+        "400":
+          description: Invalid request (e.g. username already exists).
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorResponse'
+        "401":
+          description: Not authenticated.
+        "403":
+          description: Forbidden (admin only).
+        "404":
+          description: User not found.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorResponse'
+    delete:
+      operationId: deleteUser
+      summary: Delete user (admin only)
+      description: Deletes a user by id. Cannot delete self or the last admin.
+      tags:
+        - users
+      parameters:
+        - $ref: '#/components/parameters/UserId'
+      responses:
+        "204":
+          description: User deleted.
+        "400":
+          description: Cannot delete self or last admin.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorResponse'
+        "401":
+          description: Not authenticated.
+        "403":
+          description: Forbidden (admin only).
+        "404":
+          description: User not found.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/ErrorResponse'
+
 components:
 
   parameters:
@@ -519,6 +610,14 @@ components:
       schema:
         type: string
         format: uuid
+    UserId:
+      name: userId
+      in: path
+      required: true
+      description: Unique identifier of the user (UUID).
+      schema:
+        type: string
+        format: uuid
 
   schemas:
 
@@ -1117,6 +1216,20 @@ components:
         - username
         - roles
 
+    ChangePasswordRequest:
+      type: object
+      description: Request to change the current user's password.
+      properties:
+        currentPassword:
+          type: string
+          description: Current plain-text password (verified before change).
+        newPassword:
+          type: string
+          description: New plain-text password (hashed on server).
+      required:
+        - currentPassword
+        - newPassword
+
     UserSummary:
       type: object
       description: User without password (for list and create response).
@@ -1163,6 +1276,26 @@ components:
         - password
         - role
 
+    UpdateUserRequest:
+      type: object
+      description: Request to update an existing user (admin only). Password optional; omit to keep current.
+      properties:
+        username:
+          type: string
+          description: Login name.
+        password:
+          type: string
+          description: Optional new plain-text password (omit or blank to keep current).
+        role:
+          type: string
+          enum:
+            - admin
+            - user
+          description: Role to assign.
+      required:
+        - username
+        - role
+
     # ─── Error ────────────────────────────────────────────────────────────────
 
     ErrorResponse: