feat: add admin views for federation configuration, hosts and users (#11115)

Fixes #9282

Adds a new admin panel category for federation related administration.

Includes views for:
- Instance Federation Configuration
- List of Federation Hosts
- (Per-Instance) List of Federated Users

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11115
Reviewed-by: elle <0xllx0@noreply.codeberg.org>
Reviewed-by: Panagiotis "Ivory" Vasilopoulos <git@n0toose.net>
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Florian Pallas <mail@fpallas.com>
Co-committed-by: Florian Pallas <mail@fpallas.com>

services/context/context.go

@@ -184,6 +184,7 @@ func Contexter() func(next http.Handler) http.Handler {
 			ctx.Data["DisableStars"] = setting.Repository.DisableStars
 			ctx.Data["DisableForks"] = setting.Repository.DisableForks
 			ctx.Data["EnableActions"] = setting.Actions.Enabled
+			ctx.Data["EnableFederation"] = setting.Federation.Enabled
 
 			ctx.Data["UnitWikiGlobalDisabled"] = unit.TypeWiki.UnitGlobalDisabled()
 			ctx.Data["UnitIssuesGlobalDisabled"] = unit.TypeIssues.UnitGlobalDisabled()