Remove /self endpoints and implement a new available API Endpoint

Issue Description

Remove all /self Endpoints and implement a new available API Endpoint across all repos.

List

1. • /user/self/intro

• Reference: https://github.com/Real-Dev-Squad/website-backend/pull/2293

2. • /trade/stock/new/self

• Reference: https://github.com/Real-Dev-Squad/website-backend/pull/2299

3. • /extension-requests/self

• Reference: https://github.com/Real-Dev-Squad/website-backend/pull/2300

4. • /tasks/assign/self

• Reference: https://github.com/Real-Dev-Squad/website-backend/pull/2317

5. • /users/self PATCH

• Reference: https://github.com/Real-Dev-Squad/website-backend/pull/2316

6. • /tasks/self/:id

• Reference: https://github.com/Real-Dev-Squad/website-backend/pull/2320

7. • /tasks/self

• Reference: https://github.com/Real-Dev-Squad/website-backend/pull/2284

Below is the mentioned list of repos where /self is currently being used for each route individually:

1. • [ ]
2. • [ ]

Expected Behavior

We should have removed the usage of the /self API Endpoint and should be using the new API endpoints.

Current Behavior

Currently, we are using the /self API Endpoint.

Screenshots

Reproducibility

• This issue is reproducible
• This issue is not reproducible

Steps to Reproduce

1. Go to every repo and check where we use and call /self Endpoints.

Severity/Priority

• Critical
• High
• Medium
• Low

Additional Information

Checklist

• I have read and followed the project's code of conduct.
• I have searched for similar issues before creating this one.
• I have provided all the necessary information to understand and reproduce the issue.
• I am willing to contribute to the resolution of this issue.