Azure token provider with support for Managed Identities (#33807)

* Azure token provider

* Configuration for Azure token provider

* Authentication via Azure SDK for Go

* Fix typo

* ConcurrentTokenCache for Azure credentials

* Resolve AAD authority for selected Azure cloud

* Fixes

* Generic AccessToken and fixes

* Tests and wordings

* Tests for getAccessToken

* Tests for getClientSecretCredential

* Tests for token cache

pkg/api/pluginproxy/ds_proxy.go

@@ -231,7 +231,7 @@ func (proxy *DataSourceProxy) director(req *http.Request) {
 	req.Header.Del("Referer")
 
 	if proxy.route != nil {
-		ApplyRoute(proxy.ctx.Req.Context(), req, proxy.proxyPath, proxy.route, proxy.ds)
+		ApplyRoute(proxy.ctx.Req.Context(), req, proxy.proxyPath, proxy.route, proxy.ds, proxy.cfg)
 	}
 
 	if oauthtoken.IsOAuthPassThruEnabled(proxy.ds) {