Fix modal displaying and add image to application entity.

cerberus/src/app/core/services/modal.service.ts

@@ -0,0 +1,21 @@
+import { Injectable, Type } from "@angular/core";
+import { BehaviorSubject, Observable } from "rxjs";
+
+@Injectable({
+    providedIn: 'root'
+})
+export class ModalService {
+    _modalContent: BehaviorSubject<Type<unknown> | undefined> = new BehaviorSubject<Type<unknown> | undefined>(undefined);
+
+    open(componentClass: Type<unknown>): void {
+        this._modalContent.next(componentClass);
+    }
+
+    close(): void {
+        this._modalContent.next(undefined);
+    }
+
+    get modalContent(): Observable<Type<unknown> | undefined> {
+        return this._modalContent.asObservable();
+    }
+}