fix: proxy policies middleware tus filename evaluation

when uploading files via uppy (tus), the path does not give any information about the file, PUT contains the filename in the path, tus POST not.

this pr extracts the HeaderUploadMetadata from that POST request and enhances the policies grpc environment request with that information.

Therefore, the policies service is now able to evaluate proxy requests for tus uploads too.

go.mod

@@ -65,7 +65,7 @@ require (
 	github.com/onsi/ginkgo v1.16.5
 	github.com/onsi/ginkgo/v2 v2.9.1
 	github.com/onsi/gomega v1.27.4
-	github.com/open-policy-agent/opa v0.50.2
+	github.com/open-policy-agent/opa v0.51.0
 	github.com/orcaman/concurrent-map v1.0.0
 	github.com/owncloud/libre-graph-api-go v1.0.2-0.20230330145712-ea267ccd404a
 	github.com/pkg/errors v0.9.1
@@ -184,7 +184,7 @@ require (
 	github.com/go-git/go-git/v5 v5.4.2 // indirect
 	github.com/go-kit/log v0.2.1 // indirect
 	github.com/go-logfmt/logfmt v0.5.1 // indirect
-	github.com/go-logr/logr v1.2.3 // indirect
+	github.com/go-logr/logr v1.2.4 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-resty/resty/v2 v2.7.0 // indirect
 	github.com/go-sql-driver/mysql v1.6.0 // indirect