[MM-586] Added API token for fetching issue details

[raghavaggarwal2308]

Summary

1. Added API token field in system console.
2. Added logic to fetch issue details with API token(if set in system console) for comment and issue created events.

Screenshot

What to test?

1. API token set: Notifications are getting delivered for all event, evne if the user triggering the event in not connected.
2. API token not set: Notification are delivered only if the user triggering the event is connected on mattermost.

How to test:

1. Connect your Jira account.
2. Set the API token in settings. (How to create API token)
3. Trigger the desired event from Jira.
   Note: API token is preferred to be created using an admin Jira account. Otherwise notification will not be delivered for the project the API token user do not have access to.

[ayusht2810]

Suggested change

	"help_text": "This token is used to fetch some extra details for a Jira issue for comment related and 'issue created' subscription events.",
	"help_text": "This token is used to fetch some extra details for a Jira issue for 'comment related' and 'issue created' subscription events.",

[ayusht2810]

Also, this isn't matching with the description of what to test? Shouldn't we update it to something like Set this token to view notifications when the user is not connected?

We should add the note here as mentioned in the description: API token is preferred to be created using an admin Jira account. Otherwise, notification will not be delivered for the project the API token user does not have access to.

Also, can we add this somewhere in readme or link here itself, on how to generate this token?

[raghavaggarwal2308]

@ayusht2810 Updated the help test. We will add documentation for this PR once the PR is approved

[AayushChaudhary0001]

While testing this PR, I found an issue regarding the notifications. When the user who triggers the event is not connected but the API token is set for the instance, the user receives the notification. But when the API token is not set and the user is not connected, still the notifications are getting delivered on Mattermost instance.
Note:- I have tested this with triggering the event on Jira with the same account which is connected to MM.

[AayushChaudhary0001]

While testing this PR, I have experienced an issue which was making plugin to crash. While triggering an event to receive a notification on MM, the plugin creates a panic(as visible in the logs) which crashes the plugin. Please refer the logs below:-

[raghavaggarwal2308]

@AayushChaudhary0001 The above panic issue should be fixed now. Can you please re-test the PR.

[AayushChaudhary0001]

The PR has been tested for the below conditions:-

• Notification received if the user is connected.
• Notifications for issue created and comment fit he user is not connected but the API token is set.

The PR is working fine for the above conditions, LGTM. Approved.