Allow Token API calls be authorized using the reverse-proxy header (#15119)

* API calls authorized with HTTP header

This mod allows API calls to be authorized with HTTP header
when ENABLE_REVERSE_PROXY_AUTHENTICATION is enabled. Without
it user authenticated by reverse proxy is able to access
gitea UI but not API which is inconsistent.

Author-Change-Id: IB#1107572

* Fixed API calls authorized with HTTP header

Only reqBasicAuth is modified to allow reverse proxy
auth as alternative and reqToken is left untouched.

Fixes: dc952c063206d11504085ddea966f121e796a04c
Author-Change-Id: IB#1107572

* Reverse proxy API auth separated in docs

Related: https://github.com/go-gitea/gitea/pull/15119#discussion_r621322127
Author-Change-Id: IB#1107572

* Reverse proxy API auth separated in docs

Related: https://github.com/go-gitea/gitea/pull/15119#discussion_r621322127
Author-Change-Id: IB#1107572

* Reverse proxy API auth separated

Related: https://github.com/go-gitea/gitea/pull/15119#discussion_r621322127
Author-Change-Id: IB#1107572

* ReverseProxyAuth removed from swagger

ReverseProxyAuth removed from swagger as in upstream's suggestion.

Related: https://github.com/go-gitea/gitea/pull/15119#pullrequestreview-692180940
Author-Change-Id: IB#1107572

* ReverseProxyAuth API authorization fixed

Related: https://github.com/go-gitea/gitea/pull/15119#issuecomment-868465099
Author-Change-Id: IB#1107572

* ReverseProxyAuth API authorization fixed

Related: https://github.com/go-gitea/gitea/pull/15119#issuecomment-868465099
Author-Change-Id: IB#1107572

routers/api/v1/api.go

@@ -215,10 +215,13 @@ func reqExploreSignIn() func(ctx *context.APIContext) {
 	}
 }
 
-func reqBasicAuth() func(ctx *context.APIContext) {
+func reqBasicOrRevProxyAuth() func(ctx *context.APIContext) {
 	return func(ctx *context.APIContext) {
+		if ctx.IsSigned && setting.Service.EnableReverseProxyAuth && ctx.Data["AuthedMethod"].(string) == new(auth.ReverseProxy).Name() {
+			return
+		}
 		if !ctx.Context.IsBasicAuth {
-			ctx.Error(http.StatusUnauthorized, "reqBasicAuth", "basic auth required")
+			ctx.Error(http.StatusUnauthorized, "reqBasicOrRevProxyAuth", "auth required")
 			return
 		}
 		ctx.CheckForOTP()
@@ -630,7 +633,7 @@ func Routes(sessioner func(http.Handler) http.Handler) *web.Route {
 					m.Combo("").Get(user.ListAccessTokens).
 						Post(bind(api.CreateAccessTokenOption{}), user.CreateAccessToken)
 					m.Combo("/{id}").Delete(user.DeleteAccessToken)
-				}, reqBasicAuth())
+				}, reqBasicOrRevProxyAuth())
 			})
 		})