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>

cmd/admin.go

@@ -372,6 +372,15 @@ var (
 			Value: "",
 			Usage: "Group Claim value for restricted users",
 		},
+		cli.StringFlag{
+			Name:  "group-team-map",
+			Value: "",
+			Usage: "JSON mapping between groups and org teams",
+		},
+		cli.BoolFlag{
+			Name:  "group-team-map-removal",
+			Usage: "Activate automatic team membership removal depending on groups",
+		},
 	}
 
 	microcmdAuthUpdateOauth = cli.Command{
@@ -853,6 +862,8 @@ func parseOAuth2Config(c *cli.Context) *oauth2.Source {
 		GroupClaimName:                c.String("group-claim-name"),
 		AdminGroup:                    c.String("admin-group"),
 		RestrictedGroup:               c.String("restricted-group"),
+		GroupTeamMap:                  c.String("group-team-map"),
+		GroupTeamMapRemoval:           c.Bool("group-team-map-removal"),
 	}
 }
 
@@ -935,6 +946,12 @@ func runUpdateOauth(c *cli.Context) error {
 	if c.IsSet("restricted-group") {
 		oAuth2Config.RestrictedGroup = c.String("restricted-group")
 	}
+	if c.IsSet("group-team-map") {
+		oAuth2Config.GroupTeamMap = c.String("group-team-map")
+	}
+	if c.IsSet("group-team-map-removal") {
+		oAuth2Config.GroupTeamMapRemoval = c.Bool("group-team-map-removal")
+	}
 
 	// update custom URL mapping
 	customURLMapping := &oauth2.CustomURLMapping{}