Change the GitHub PR template to automatically link PRs to tickets in ZenHub

[benbowler]

Feature Description

While reading the ZenHub docs about connecting PRs to tickets I came across this:

The simplest method is using GitHub's closing keywords when creating pull requests. When you include phrases like "Fixes #123", "Closes #456", or "Resolves #789" in your PR description,

If we update our PR template to include "Fixes #", then PRs will be automatically linked helping us to make sure we don't miss this.

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Acceptance criteria

• PRs should automatically be connected to issues in ZenHub if the template is followed.

Implementation Brief

• Review and merge the attached PR

Test Coverage

• N/A

QA Brief

• No QA Required.

Changelog entry

[nfmohit]

@benbowler As far as I can remember, using GitHub's closing keywords closes the issue when the PR is merged, which is not in line with our pipeline workflow, where an issue goes through QA and Approval before it is closed. Have you considered this behaviour?

[benbowler]

@nfmohit i hadn't. I tried this on #11899 manually, so we can see if this causes undesired behaviour.