[GH-400] Display proper message for access request todo

[raghavaggarwal2308]

Summary

The description of the "member_access_requested" todo was not being displayed, we handled the case specifically and added a proper description.

Screenshots

Earlier:

Now:

What to test:

• Todos are properly displayed for "member_access_requested".

Steps to reproduce:

1. Connect your Gitlab account.
2. Request access to one of your projects/groups from any other user. You will get a todo/notification on Gitlab for access request.
3. Run the /gitlab todo command on Mattermost. You should get a post containing the todos.

Expected behavior:

• The "member_access_requested" todo should have a proper description.

Environment:

GitLab Plugin version: 1.7.0
MM version: v7.8.2

Ticket Link

Fixes #400

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (7190bfd) 32.91% compared to head (3fa37a3) 32.86%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #404      +/-   ##
==========================================
- Coverage   32.91%   32.86%   -0.05%     
==========================================
  Files          22       22              
  Lines        4017     4022       +5     
==========================================
  Hits         1322     1322              
- Misses       2564     2569       +5     
  Partials      131      131              

Files	Coverage Δ
server/plugin.go	14.28% <0.00%> (-0.11%)	⬇️

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[mickmister]

LGTM 👍 Just some naming suggestions

[raghavaggarwal2308]

@mickmister Fixed the review comments mentioned by you.

[AayushChaudhary0001]

Tested and approved, LGTM