feat: edit an existing custom type

web/src/components/FieldInspector.vue

@@ -154,6 +154,8 @@ watch(
 				/>
 			</DirectoryField>
 			<SlugField
+				:locked="field.saved"
+				:locked-help="t('Used in the API, so it can\'t change.')"
 				:label="t('Key')"
 				name="field-key"
 				:mode="keyMode"
@@ -180,6 +182,7 @@ watch(
 			:model-value="type"
 			:compact="compact"
 			:disabled="disabled"
+			:locked="field.saved"
 			@update:model-value="emit('type', $event)"
 		/>