POST request for JOIN table - rest

Question

Let's say 3 tables
session
-------------------------
id | name | date
-------------------------
speaker
-------------------------
id | name
-------------------------
session_speaker
-------------------------
session_id | speaker_id
-------------------------
I've endpoints already in place to do the insertion
POST /session
POST /speaker
What kind of REST request should I create to specify the intention to insert into the JOIN table using POST /session or any other method (passing session_id and speaker_id)
Note: I've a PATCH request already in place to activate or deactivate a session.
Question:
Basically seeking an ideal REST based solution to handle CRUD based operations for the JOIN table, please advise.

Answer 1

You could use the following REST operation for creating the relationship:
PUT speakers/speaker/{speakerId}/session/{sessionId}/
I don't advise using plural names in URLs (e.g. speakers), I'd recommend a singular name such as SessionSpeaker, but as you can't change it from "speakers" I've used it as requested.
You should also use PUT instead of POST for inserting data, as PUT is idempotent i.e. PUT guards against you inserting the same speaker at a session.
To then retrieve speakers information you could use:
GET speakers/session/{sessionId}
GET speakers/speaker/{speakerId}
Another good answer regarding REST and entity multiplicity is here.