[GH-626]: Supported filtering on comment visibility for subscriptions

[Nityanand13]

Summary

Added "Comment Visibility" field to subscription modal to filter notifications in the channel.

1. When a user creates a comment in Jira then the plugin is getting notified through a webhook. Now, with this API we are getting all the information of a comment. If that particular comment has a visibility attribute that it should be visible to the users who belong to a certain group. Then notification is sent to the subscribed channel in mattermost only when that particular group is included in the subscriptions and vice versa.
2. Apart from adding groups to which a user belongs, he can also add a group ‘visible-to-all-users’. If a particular comment has no visibility attribute, then notification is sent to the subscribed channel in mattermost only when ‘visible-to-all-users’ is present or no filter is present on the mattermost side.

Ticket Link

Fixes #626

[mattermod]

Hello @Nityanand13,

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[mattermod]

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[hanzei]

@mickmister Head up that the PR is ready for your review

[mattermost-build]

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 5.47945% with 69 lines in your changes missing coverage. Please review.

Project coverage is 29.41%. Comparing base (3d90500) to head (649d520). Report is 10 commits behind head on master.

:exclamation: Current head 649d520 differs from pull request most recent head 5e21750

Please upload reports for the commit 5e21750 to get more accurate results.

Files	Patch %	Lines
server/issue.go	0.00%	34 Missing :warning:
server/webhook_worker.go	0.00%	23 Missing :warning:
server/client.go	0.00%	7 Missing :warning:
server/subscribe.go	37.50%	3 Missing and 2 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #894      +/-   ##
==========================================
- Coverage   33.37%   29.41%   -3.97%     
==========================================
  Files          53       52       -1     
  Lines        8008     7861     -147     
==========================================
- Hits         2673     2312     -361     
- Misses       5112     5351     +239     
+ Partials      223      198      -25     

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[Kshitij-Katiyar]

@mickmister Fixed the merge conflicts and this PR is ready for review.

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity. A core team member will check in on the status of the PR to help with questions. Thank you for your contribution!

[mickmister]

Also this will need to be tested on Jira Cloud and Jira Server

[raghavaggarwal2308]

@mickmister Fixed the review comments added by you.

[mattermost-build]

This PR has been automatically labelled "stale" because it hasn't had recent activity. A core team member will check in on the status of the PR to help with questions. Thank you for your contribution!