Prettied, Linted and updated angular.json according to the latest schematic of Angular CLI.

Now all that is needed is to make it ready for strict compiling.
Removed eslint-plugin-prettier as it is not recommended and causes errors for both eslint and prettier

Bumped to v8.0.0

overlord/src/app/purchase-entries/purchase-entries.service.ts

@@ -1,13 +1,11 @@
+import { HttpClient } from '@angular/common/http';
 import { Injectable } from '@angular/core';
-import { catchError } from 'rxjs/operators';
 import { Observable } from 'rxjs/internal/Observable';
-import { HttpClient, HttpHeaders, HttpParams } from '@angular/common/http';
-import { PurchaseEntries } from './purchase-entries';
+import { catchError } from 'rxjs/operators';
+
 import { ErrorLoggerService } from '../core/error-logger.service';
 
-const httpOptions = {
-  headers: new HttpHeaders({ 'Content-Type': 'application/json' }),
-};
+import { PurchaseEntries } from './purchase-entries';
 
 const url = '/api/purchase-entries';
 const serviceName = 'PurchaseEntriesService';
@@ -19,11 +17,11 @@ export class PurchaseEntriesService {
   constructor(private http: HttpClient, private log: ErrorLoggerService) {}
 
   list(startDate: string, finishDate): Observable<PurchaseEntries> {
-    startDate = startDate ? `/${startDate}` : '';
-    finishDate = finishDate ? `/${finishDate}` : '';
+    const startDateWithSlash = startDate ? `/${startDate}` : '';
+    const finishDateWithSlash = finishDate ? `/${finishDate}` : '';
     return <Observable<PurchaseEntries>>(
       this.http
-        .get<PurchaseEntries>(`${url}${startDate}${finishDate}`)
+        .get<PurchaseEntries>(`${url}${startDateWithSlash}${finishDateWithSlash}`)
         .pipe(catchError(this.log.handleError(serviceName, 'list')))
     );
   }