Return 400 error when upload invalid maven package

Right now we return 500 error if user tries to upload maven package with
invalid version. This commit will rescue exception and return 400 error.
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

ee/changelogs/unreleased/8793-gitlab-returns-500-when-maven-package-metadata-validation-regex-fails.yml

+---
+title: Return 400 error instead of 500 when upload maven package with invalid version
+merge_request: 9125
+author:
+type: fixed

ee/lib/api/maven_packages.rb

@@ -9,6 +9,10 @@ module API
     content_type :sha1, 'text/plain'
     content_type :binary, 'application/octet-stream'
 
+    rescue_from ActiveRecord::RecordInvalid do |e|
+      render_api_error!(e.message, 400)
+    end
+
     before do
       require_packages_enabled!
       authenticate_non_get!

ee/spec/requests/api/maven_packages_spec.rb

@@ -10,6 +10,7 @@ describe API::MavenPackages do
   let(:headers) { { 'GitLab-Workhorse' => '1.0', Gitlab::Workhorse::INTERNAL_API_REQUEST_HEADER => jwt_token } }
   let(:headers_with_token) { headers.merge('Private-Token' => personal_access_token.token) }
   let(:job) { create(:ci_build, user: user) }
+  let(:version) { '1.0-SNAPSHOT' }
 
   before do
     project.add_developer(user)
@@ -345,7 +346,7 @@ describe API::MavenPackages do
     end
 
     def authorize_upload(params = {}, request_headers = headers)
-      put api("/projects/#{project.id}/packages/maven/com/example/my-app/1.0-SNAPSHOT/maven-metadata.xml/authorize"), params: params, headers: request_headers
+      put api("/projects/#{project.id}/packages/maven/com/example/my-app/#{version}/maven-metadata.xml/authorize"), params: params, headers: request_headers
     end
 
     def authorize_upload_with_token(params = {}, request_headers = headers_with_token)
@@ -405,10 +406,21 @@ describe API::MavenPackages do
 
         expect(response).to have_gitlab_http_status(200)
       end
+
+      context 'version is not correct' do
+        let(:version) { '$%123' }
+
+        it 'rejects request' do
+          expect { upload_file_with_token(params) }.not_to change { project.packages.count }
+
+          expect(response).to have_gitlab_http_status(400)
+          expect(json_response['message']).to include('Validation failed')
+        end
+      end
     end
 
     def upload_file(params = {}, request_headers = headers)
-      put api("/projects/#{project.id}/packages/maven/com/example/my-app/1.0-SNAPSHOT/maven-metadata.xml"), params: params, headers: request_headers
+      put api("/projects/#{project.id}/packages/maven/com/example/my-app/#{version}/maven-metadata.xml"), params: params, headers: request_headers
     end
 
     def upload_file_with_token(params = {}, request_headers = headers_with_token)