fix: fixed an issue with aot compilation and service factory

Author: Supamiu

src/xivapi-client.module.ts

@@ -1,9 +1,11 @@
-import { ModuleWithProviders, NgModule } from '@angular/core';
+import { InjectionToken, ModuleWithProviders, NgModule } from '@angular/core';
 import { CommonModule } from '@angular/common';
 import { XivapiService } from './xivapi.service';
 import { HttpClient, HttpClientModule } from '@angular/common/http';
 import { XivapiServiceFactory } from './xivapi-service-factory';
 
+export const XIVAPI_KEY: InjectionToken<string> = new InjectionToken('XIVAPI_KEY');
+
 @NgModule({
     imports: [
         CommonModule,
@@ -17,10 +19,14 @@ export class XivapiClientModule {
         return {
             ngModule: XivapiClientModule,
             providers: [
+                {
+                    provide: XIVAPI_KEY,
+                    useValue: key
+                },
                 {
                     provide: XivapiService,
                     useFactory: XivapiServiceFactory,
-                    deps: [key, HttpClient]
+                    deps: [XIVAPI_KEY, HttpClient]
                 }
             ]
         };

src/xivapi.service.ts

@@ -1,4 +1,4 @@
-import { Inject, Injectable, Optional } from '@angular/core';
+import { Inject, Injectable } from '@angular/core';
 import { HttpClient, HttpParams } from '@angular/common/http';
 import { Observable } from 'rxjs';
 import {
@@ -12,6 +12,7 @@ import {
     XivapiSearchOptions
 } from './model';
 import { CharacterResponse, CharacterVerification } from './model/schema/character';
+import { XIVAPI_KEY } from './xivapi-client.module';
 
 @Injectable()
 export class XivapiService {
@@ -21,7 +22,7 @@ export class XivapiService {
      */
     public static readonly API_BASE_URL: string = 'https://xivapi.com';
 
-    constructor(@Inject('XIVAPI_KEY') protected readonly apiKey: string, private http: HttpClient) {
+    constructor(@Inject(XIVAPI_KEY) protected readonly apiKey: string, private http: HttpClient) {
     }
 
     /**