Uniqueness of the "Best Response"

[Procos12]

In this issue, if we detect that a response was marked as the best response in a thread, it should be unique. Originally based on #16, but that was too many issues in one.

Estimated Effort:
With help from the team and some work with the database's logic, this shouldn't be that hard.
Around 3-4 days

Dependencies:
#40

Initial assignments for team members:
Assigned to Abdulwahab Al-Rumaihi

Milestones to indicate which sprint the issue should be completed in:
This should be complete by the end of sprint 2

Acceptance criteria:
It should work visually, upon refresh of the page only one answer should be marked as the best answer.
We will write test cases in the code.
Will be tested by the logger using print statements.