title: I get Error: Type 'Subscription' is not assignable to type 'Observable'
body: <p>Here I have my two methods in my service. I am new to this, so I am not sure what subscribe method does, but all I know I can't build my project without it. If i comment these two functions, then ng serve, then uncomment, and let it refresh changes, it works. But I can't build project. How do I change the code, so I don't get those errors and build project successfully?</p>
  
  <pre><code>public delete(patient: Patient): Observable&lt;Patient&gt; {
      return this.http.delete&lt;Patient&gt;(`${this.deleteOneUrl}/${patient.id}`).subscribe();
  }
  
  public addPatient(patient: Patient): Observable&lt;Patient&gt; {  
      return this.http.post&lt;Patient&gt;(this.addOneUrl, patient).subscribe();
  }
  </code></pre>
  
  <blockquote>
    <p>ERROR in src/app/patient.service.ts(30,3): error TS2322: Type 'Subscription' is not assignable to type 'Observable'.
      Property '_isScalar' is missing in type 'Subscription'.
    src/app/patient.service.ts(38,5): error TS2322: Type 'Subscription' is not assignable to type 'Observable'.</p>
  </blockquote>