[BE] `/pins` endpoint

[Antonov548]

Summary

We need to have and table for the pins with the following columns:

• id
• title -> string
• image -> image url
• tags -> array os string like ["cats", "cute"]
• userId
• createdAt -> now()

Endpoints

• GET -> params { pinId? }
  • returns an array of pins or only one if pinId is provided
• POST -> params { all columns necessary mentioned above }
• DELETE -> params { pinId }

AC

• create table for pin's in database
• relation with user table
• endpoint for GET/POST pin

[ls-ramos]

@Navya-Bharathan please check the PR for the task: #161

and align with @japint since his task might overlap with yours