feat: more role backend and admin/writer roles additions and adjustments

test/image_variants_cache_http_test.go

@@ -29,8 +29,8 @@ func TestImageVariantsCacheGuards(t *testing.T) {
 		{"no cookie", http.MethodGet, cacheStatsPath, "none", 401, apperr.UnauthorizedErrorMessage},
 		{"a stale token_version cookie", http.MethodGet, cacheStatsPath, "stale", 401, apperr.UnauthorizedErrorMessage},
 		{"the cookie of an unverified user", http.MethodGet, cacheStatsPath, "unverified", 403, apperr.VerificationRequiredErrorMessage},
-		{"the cookie of a plain user", http.MethodGet, cacheStatsPath, "plain", 403, apperr.OwnerOrAdminRequiredErrorMessage},
-		{"the cookie of a plain user on purge", http.MethodPost, cachePurgePath, "plain", 403, apperr.OwnerOrAdminRequiredErrorMessage},
+		{"the cookie of a plain user", http.MethodGet, cacheStatsPath, "plain", 403, apperr.MissingPermissionErrorMessage},
+		{"the cookie of a plain user on purge", http.MethodPost, cachePurgePath, "plain", 403, apperr.MissingPermissionErrorMessage},
 		{"a valid API key", http.MethodGet, cacheStatsPath, "apikey", 401, apperr.UnauthorizedErrorMessage},
 		{"a valid API key on purge", http.MethodPost, cachePurgePath, "apikey", 401, apperr.UnauthorizedErrorMessage},
 	}