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>

templates/admin/auth/edit.tmpl

@@ -361,6 +361,14 @@
 						<label for="oauth2_restricted_group">{{.locale.Tr "admin.auths.oauth2_restricted_group"}}</label>
 						<input id="oauth2_restricted_group" name="oauth2_restricted_group" value="{{$cfg.RestrictedGroup}}">
 					</div>
+					<div class="field">
+						<label>{{.locale.Tr "admin.auths.oauth2_map_group_to_team"}}</label>
+						<input name="oauth2_group_team_map" value="{{$cfg.GroupTeamMap}}" placeholder='e.g. {"Developer": {"MyGiteaOrganization": ["MyGiteaTeam1", "MyGiteaTeam2"]}}'>
+					</div>
+					<div class="ui checkbox">
+						<label>{{.locale.Tr "admin.auths.oauth2_map_group_to_team_removal"}}</label>
+						<input name="oauth2_group_team_map_removal" type="checkbox" {{if $cfg.GroupTeamMapRemoval}}checked{{end}}>
+					</div>
 				{{end}}
 
 				<!-- SSPI -->