AuthProxy: Allow disabling Auth Proxy cache (#83755)

* extract auth proxy settings

* simplify auth proxy methods

* add doc mentions

pkg/services/datasources/service/datasource.go

@@ -675,7 +675,7 @@ func (s *Service) getCustomHeaders(jsonData *simplejson.Json, decryptedValues ma
 		// skip a header with name that corresponds to auth proxy header's name
 		// to make sure that data source proxy isn't used to circumvent auth proxy.
 		// For more context take a look at CVE-2022-35957
-		if s.cfg.AuthProxyEnabled && http.CanonicalHeaderKey(key) == http.CanonicalHeaderKey(s.cfg.AuthProxyHeaderName) {
+		if s.cfg.AuthProxy.Enabled && http.CanonicalHeaderKey(key) == http.CanonicalHeaderKey(s.cfg.AuthProxy.HeaderName) {
 			continue
 		}