Add api to delete user data

[parth-07]

This PR adds API to delete user data from the database.
API description:

DELETE /user/gpa-data

Response on successfully deleting user data:

{
  success: true
}

If user data is not found then API will return with 404 HTTP error code with response body:

{
  type: NOT_FOUND,
  message: "Nothing to delete, user data not found"
}

User token should be passed in Authorization header

Closes #8

[parth-07]

@github deploy

[manorit2001]

Once the android infrastructure is done, then only will I be able to test this and suggest changes based on compatibility with android. Will keep this on hold till then, Sorry for the inconvinience

[parth-07]

Once the android infrastructure is done, then only will I be able to test this and suggest changes based on compatibility with android. Will keep this on hold till then, Sorry for the inconvinience

Oh okay, no issues :)

[manorit2001]

@github deploy