fix(oauth): Error on auth sources with spaces (#37327)

The link to authentication sources is now escaped with the QueryEscape.
This commit fixes that by unescaping the provider name in the URL.

---------

Signed-off-by: prettysunflower <me@prettysunflower.moe>
Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/auth/oauth.go

@@ -36,7 +36,9 @@ import (
 
 // SignInOAuth handles the OAuth2 login buttons
 func SignInOAuth(ctx *context.Context) {
-	authName := ctx.PathParam("provider")
+	// the provider is escaped by backend QueryEscape and frontend urlQueryEscape
+	// so always use QueryUnescape to decode it
+	authName, _ := url.QueryUnescape(ctx.PathParamRaw("provider"))
 	authSource, err := auth.GetActiveOAuth2SourceByAuthName(ctx, authName)
 	if err != nil {
 		ctx.ServerError("SignIn", err)