core: add UserSelfSerializer and separate method for users to update themselves with limited fields

rework user settings page to better use form
closes #1227

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

web/src/elements/forms/ModelForm.ts

@@ -3,17 +3,20 @@ import { EVENT_REFRESH } from "../../constants";
 import { Form } from "./Form";
 
 export abstract class ModelForm<T, PKT extends string | number> extends Form<T> {
+    viewportCheck = true;
+
     abstract loadInstance(pk: PKT): Promise<T>;
 
     @property({ attribute: false })
     set instancePk(value: PKT) {
         this._instancePk = value;
-        if (this.isInViewport) {
-            this.loadInstance(value).then((instance) => {
-                this.instance = instance;
-                this.requestUpdate();
-            });
+        if (this.viewportCheck && !this.isInViewport) {
+            return;
         }
+        this.loadInstance(value).then((instance) => {
+            this.instance = instance;
+            this.requestUpdate();
+        });
     }
 
     private _instancePk?: PKT;