Improvements to notifications/alerts: Jira+Googlechat integration & limited affected projects

Hi everyone,
my company is internally working with dependency-track, and we found it useful to have the tool create Jira tickets and post to google chat. For this, we made some additions to your project, that we think could be useful to other people out there.

In detail, we changed/added the following:
* a JiraPublisher class and jira pebble template (using the subject.affectedProjects )
* a googlechat (simple webhook) publisher that uses a special googlechat-card template (also lists affectedProjects)
* settings in back- and frontend to configure a global jira tool user and provide the publisher options
* changes to the NotificationRouter class to filter the "Limited to" projects per notification before it is passed on

Since I'm not sure whether those features are in line with the direction of the project, I'd like to get some feedback whether it's worth creating pull requests for (some of) them.

Best regards