Fix: Multiple relation requests from a user to same member

[decon-harsh]

Description

A user was able to send multiple mentorship request to the same member.

So, I added a check on relation.state and returned HTTPS.CONFLICT
Fixes #866

Type of Change:

• Code

Code/Quality Assurance Only

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Manually through postman Ran all tests

Mocks

Checklist:

• [X] My PR follows the style guidelines of this project
• [X] I have performed a self-review of my own code or materials

Code/Quality Assurance Only

• [X] My changes generate no new warnings

[codecov[bot]]

Codecov Report

Merging #994 (01393c4) into develop (8f1906e) will decrease coverage by 3.26%. The diff coverage is 83.33%.

@@             Coverage Diff             @@
##           develop     #994      +/-   ##
===========================================
- Coverage    96.14%   92.88%   -3.27%     
===========================================
  Files           96       38      -58     
  Lines         5399     2079    -3320     
===========================================
- Hits          5191     1931    -3260     
+ Misses         208      148      -60     

Impacted Files	Coverage Δ
app/api/dao/mentorship_relation.py	95.65% <75.00%> (-0.46%)	:arrow_down:
app/messages.py	100.00% <100.00%> (ø)
app/api/resources/mentorship_relation.py	96.51% <0.00%> (-1.24%)	:arrow_down:
app/api/dao/user.py	85.82% <0.00%> (-0.06%)	:arrow_down:
app/api/models/user.py	100.00% <0.00%> (ø)
app/api/api_extension.py	100.00% <0.00%> (ø)
app/api/jwt_extension.py	100.00% <0.00%> (ø)
app/api/models/mentorship_relation.py	100.00% <0.00%> (ø)
app/schedulers/delete_unverified_users_cron_job.py	100.00% <0.00%> (ø)
... and 73 more

[decon-harsh]

@vj-codes Please have a look

[epicadk]

Please add releavant tests as well

[vj-codes]

@decon-harsh any updates here?

[vj-codes]

@decon-harsh any updates?