chore: add query to fetch top level idp claim fields (#15525)

Adds an api endpoint to grab all available sync field options for IDP
sync. This is for autocomplete on idp sync forms. This is required for
organization admins to have some insight into the claim fields available
when configuring group/role sync.

coderd/userauth.go

@@ -1395,13 +1395,6 @@ func mergeClaims(a, b map[string]interface{}) map[string]interface{} {
 	return c
 }
 
-// OauthDebugContext provides helpful information for admins to debug
-// OAuth login issues.
-type OauthDebugContext struct {
-	IDTokenClaims  map[string]interface{} `json:"id_token_claims"`
-	UserInfoClaims map[string]interface{} `json:"user_info_claims"`
-}
-
 type oauthLoginParams struct {
 	User      database.User
 	Link      database.UserLink