Add ability to set custom field to video form

shared/models/plugins/register-client-form-field.model.ts

@@ -0,0 +1,12 @@
+export interface RegisterClientFormFieldOptions {
+  name: string
+  label: string
+  type: 'input' | 'input-checkbox' | 'input-textarea' | 'markdown-text' | 'markdown-enhanced'
+
+  // Default setting value
+  default?: string | boolean
+}
+
+export interface RegisterClientVideoFieldOptions {
+  type: 'import-url' | 'import-torrent' | 'update' | 'upload'
+}