introduce an authentication service and prepare user management

src/auth/auth.service.ts

@@ -0,0 +1,72 @@
+import { HttpService } from '@nestjs/axios';
+import { HttpException, Injectable } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { JwtService } from '@nestjs/jwt';
+import { InjectModel } from '@nestjs/mongoose';
+import { Model } from 'mongoose';
+import { catchError, lastValueFrom, map } from 'rxjs';
+
+import { UserDocument } from './models/user.model';
+
+@Injectable()
+export class AuthService {
+  constructor(
+    @InjectModel('user')
+    private readonly userModel: Model<UserDocument>,
+    private config: ConfigService,
+    private httpService: HttpService,
+    private jwtService: JwtService,
+  ) {}
+
+  async login(code: string): Promise<string> {
+    const token = await lastValueFrom(
+      this.httpService
+        .post(
+          `${this.config.get<string>(
+            'vatsim-auth.base-url',
+          )}/${this.config.get<string>('vatsim-auth.token-endpoint')}`,
+          {
+            grant_type: 'authorization_code',
+            client_id: this.config.get<string>('vatsim-auth.client-id'),
+            client_secret: this.config.get<string>('vatsim-auth.client-secret'),
+            redirect_uri: 'http://localhost:3000/auth/vatsim',
+            code,
+          },
+        )
+        .pipe(
+          map((response) => response.data.access_token),
+          catchError((err) => {
+            throw new HttpException(err.response.data, err.response.status);
+          }),
+        ),
+    );
+
+    const userdata = await lastValueFrom(
+      this.httpService
+        .get(
+          `${this.config.get<string>(
+            'vatsim-auth.base-url',
+          )}/${this.config.get<string>('vatsim-auth.user-endpoint')}`,
+          {
+            headers: {
+              Authorization: `Bearer ${token}`,
+              Accept: 'application/json',
+            },
+          },
+        )
+        .pipe(
+          map((response) => response.data.data),
+          catchError((err) => {
+            throw new HttpException(err.response.data, err.response.status);
+          }),
+        ),
+    );
+
+    if (userdata.oauth.token_valid) {
+      const payload = { username: userdata.cid, sub: token };
+      return this.jwtService.sign(payload);
+    }
+
+    return undefined;
+  }
+}