Map OIDC groups to Orgs/Teams (#21441)

Fixes #19555

Test-Instructions:
https://github.com/go-gitea/gitea/pull/21441#issuecomment-1419438000

This PR implements the mapping of user groups provided by OIDC providers
to orgs teams in Gitea. The main part is a refactoring of the existing
LDAP code to make it usable from different providers.

Refactorings:
- Moved the router auth code from module to service because of import
cycles
- Changed some model methods to take a `Context` parameter
- Moved the mapping code from LDAP to a common location

I've tested it with Keycloak but other providers should work too. The
JSON mapping format is the same as for LDAP.


![grafik](https://user-images.githubusercontent.com/1666336/195634392-3fc540fc-b229-4649-99ac-91ae8e19df2d.png)

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

routers/web/repo/issue_label.go

@@ -78,7 +78,7 @@ func RetrieveLabels(ctx *context.Context) {
 		}
 		ctx.Data["OrgLabels"] = orgLabels
 
-		org, err := organization.GetOrgByName(ctx.Repo.Owner.LowerName)
+		org, err := organization.GetOrgByName(ctx, ctx.Repo.Owner.LowerName)
 		if err != nil {
 			ctx.ServerError("GetOrgByName", err)
 			return