added post request to achieve login response with tokens

backend/src/main/java/com/vaessl/app/exception/GlobalExceptionHandler.java

@@ -0,0 +1,40 @@
+package com.vaessl.app.exception;
+
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ProblemDetail;
+import org.springframework.web.bind.MethodArgumentNotValidException;
+import org.springframework.web.bind.annotation.ExceptionHandler;
+import org.springframework.web.bind.annotation.RestControllerAdvice;
+import org.springframework.web.client.HttpClientErrorException;
+import org.springframework.web.client.HttpServerErrorException;
+import org.springframework.web.client.ResourceAccessException;
+
+@RestControllerAdvice
+public class GlobalExceptionHandler {
+
+    @ExceptionHandler(MethodArgumentNotValidException.class)
+    public ProblemDetail handleEmptyCredentialInput(MethodArgumentNotValidException e) {
+        return ProblemDetail.forStatusAndDetail(HttpStatus.BAD_REQUEST, "Fields must not be empty.");
+    }
+
+    @ExceptionHandler(HttpClientErrorException.Unauthorized.class)
+    public ProblemDetail handleUnauthorizedAccess(HttpClientErrorException e) {
+
+        return ProblemDetail.forStatusAndDetail(HttpStatus.UNAUTHORIZED, "Invalid username or password.");
+    }
+
+    @ExceptionHandler(ResourceAccessException.class)
+    public ProblemDetail handleNoConnection(ResourceAccessException e) {
+
+        return ProblemDetail.forStatusAndDetail(HttpStatus.SERVICE_UNAVAILABLE, "The target URL is unreachable.");
+    }
+
+    @ExceptionHandler(HttpServerErrorException.class)
+    public ProblemDetail handleTimeoutOrNotFound(HttpServerErrorException e) {
+
+        return ProblemDetail
+                .forStatusAndDetail(e.getStatusCode(),
+                        "The external app returned a server error: " + e.getStatusText());
+    }
+
+}