[management] Fetch complete user data in ValidateTunnelPeer (#6457)

* [management] Fetch complete user data in ValidateTunnelPeer

Previously the `ValidateTunnelPeer` method used by the ProxyService
would fetch user information from the database if the connected peer
was associated with a user ID, but it would not consult the IdP data
for cached info from JWT claims like email.  This caused the value of
the injected `X-Netbird-User` header to always display the peer ID and
never the user email associated with the peer as expected.

This change adds an optional IdP manager to the ProxyService and
fetches the complete user data from it if present.

* [management] Refactor ValidateTunnelPeer principal info gathering

This refactors the gathering of info on proxy tunnel peer principals
into its own method to keep the complexity down and make Sonar happy.

proxy/management_byop_integration_test.go

@@ -125,6 +125,7 @@ func setupBYOPIntegrationTest(t *testing.T) *byopTestSetup {
 		oidcConfig,
 		nil,
 		usersManager,
+		nil,
 		realProxyManager,
 		nil,
 	)

proxy/management_integration_test.go

@@ -140,6 +140,7 @@ func setupIntegrationTest(t *testing.T) *integrationTestSetup {
 		oidcConfig,
 		nil,
 		usersManager,
+		nil,
 		proxyManager,
 		nil,
 	)