Added API call for algorithms (Exareme)

api/src/engine/connectors/datashield/main.connector.ts

 import { HttpService } from "@nestjs/axios";
+import { Observable } from "rxjs";
 import { IEngineOptions, IEngineService } from "src/engine/engine.interfaces";
 
 export default class DataShieldService implements IEngineService {
     constructor(private readonly options: IEngineOptions, private readonly httpService: HttpService) { }
 
+    getAlgorithms(): Observable<string> {
+        throw new Error("Method not implemented.");
+    }
+
     demo(): string {
         return "datashield";
     }

api/src/engine/connectors/exareme/main.connector.ts

 import { HttpService } from "@nestjs/axios";
+import { map, Observable } from "rxjs";
 import { IEngineOptions, IEngineService } from "src/engine/engine.interfaces";
 
 export default class ExaremeService implements IEngineService {
     constructor(private readonly options: IEngineOptions, private readonly httpService: HttpService) { }
 
+    getAlgorithms(): Observable<string> {
+        const path = this.options.baseurl + "algorithms";
+        
+        return this.httpService.get<string>(path).pipe(
+            map(response => response.data)
+        );
+    }
+
     demo(): string {
         return "exareme"
     }

api/src/engine/engine.controller.ts

 import { HttpService } from '@nestjs/axios';
 import { Controller, Get, Inject } from '@nestjs/common';
+import { Observable } from 'rxjs';
 import { ENGINE_SERVICE } from './engine.constants';
 import { IEngineService } from './engine.interfaces';
 
@@ -11,4 +12,9 @@ export class EngineController {
   getTest(): string {
     return this.engineService.demo();
   }
+
+  @Get('/algorithms')
+  getAlgorithms(): Observable<string> {
+    return this.engineService.getAlgorithms();
+  }
 }

api/src/engine/engine.interfaces.ts

+import { Observable } from "rxjs";
+
 export interface IEngineOptions {
     type: string;
+    baseurl: string;
 }
 
 export interface IEngineService {
     demo(): string;
+
+    getAlgorithms(): Observable<string>;
 }
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