Fixing OpenApi descriptions

application/module-certificate/src/main/java/org/fuseri/modulecertificate/certificate/CertificateController.java

@@ -43,7 +43,7 @@ public class CertificateController {
             description = "Generates certificate, saves it into database and returns certificate information and certificate file.")
     @ApiResponses(value = {
             @ApiResponse(responseCode = "201", description = "Certificate generated successfully."),
-            @ApiResponse(responseCode = "500", description = "Invalid input.")
+            @ApiResponse(responseCode = "500", description = "Internal server error.")
     })
     @PostMapping
     public ResponseEntity<CertificateSimpleDto> generate(@Valid @RequestBody CertificateCreateDto certificateCreateDto) {
@@ -77,7 +77,7 @@ public class CertificateController {
     @Operation(summary = "Get certificates for user", description = "Returns certificates for given user in list.")
     @ApiResponses(value = {
             @ApiResponse(responseCode = "200", description = "Successfully retrieved certificates"),
-            @ApiResponse(responseCode = "500", description = "Invalid input."),
+            @ApiResponse(responseCode = "500", description = "Internal server error."),
     })
     @GetMapping("/findForUser")
     public ResponseEntity<List<CertificateSimpleDto>> findForUser(@RequestParam Long userId) {
@@ -96,7 +96,7 @@ public class CertificateController {
             description = "Returns certificates for given user and course in list.")
     @ApiResponses(value = {
             @ApiResponse(responseCode = "200", description = "Successfully retrieved certificates"),
-            @ApiResponse(responseCode = "500", description = "Invalid input."),
+            @ApiResponse(responseCode = "500", description = "Internal server error."),
     })
     @GetMapping("/findForUserAndCourse")
     public ResponseEntity<List<CertificateSimpleDto>> findForUserAndCourse(@RequestParam Long userId, @RequestParam Long courseId) {
@@ -111,6 +111,7 @@ public class CertificateController {
     @Operation(summary = "Delete a certificate with specified ID", description = "Deletes a certificate with the specified ID.")
     @ApiResponses(value = {
             @ApiResponse(responseCode = "204", description = "Certificate with the specified ID deleted successfully."),
+            @ApiResponse(responseCode = "500", description = "Internal server error.")
     })
     @DeleteMapping("/{id}")
     public ResponseEntity<Void> delete(@NotNull @PathVariable Long id) {
@@ -126,7 +127,7 @@ public class CertificateController {
     @Operation(summary = "Get certificates in paginated format", description = "Returns certificates in paginated format.")
     @ApiResponses(value = {
             @ApiResponse(responseCode = "200", description = "Successfully retrieved paginated certificates"),
-            @ApiResponse(responseCode = "500", description = "Invalid page number supplied"),
+            @ApiResponse(responseCode = "500", description = "Internal server error.")
     })
     @GetMapping
     public ResponseEntity<Page<CertificateSimpleDto>> findAllCertificates(Pageable pageable) {