Allow multiple metadata files for Maven packages (#20674)

* Allow file overwrite for meta files.

* Added tests.

* lint

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

routers/api/packages/maven/maven.go

@@ -266,8 +266,9 @@ func UploadPackageFile(ctx *context.Context) {
 		PackageFileInfo: packages_service.PackageFileInfo{
 			Filename: params.Filename,
 		},
-		Data:   buf,
-		IsLead: false,
+		Data:              buf,
+		IsLead:            false,
+		OverwriteExisting: params.IsMeta,
 	}
 
 	// If it's the package pom file extract the metadata