Generate pull request title from issue title

The current "Create pull request" button available under a JIRA issue will create a GitHub pull request where the PR's title will be generated from the branch name. E.g. for a branch named "issue/KEY-123" the PR title will be "Issue/key 123" (note the different casing and lack of dash).

Instead of this (possibly as an option), the PR's title could come from the title of the issue, concatenated with its issue key. E.g. "KEY-123 Implementing awesome feature". This way we'd a) get an actual legible title for the PR right off the bat instead of having to edit it all the time and b) the PR would be connected to the JIRA issue (I think unless the issue key is mentioned in the PR title it won't show up under the issue, just the branch).

As an added super-awesomeness the body of the PR could be auto-populated too, also referencing the JIRA issue. This could be something like "Click here for the corresponding JIRA issue." that would link to the issue. This way you could not just reach the PR from the issue easily but also the other way around.

Start by tracing the Create pull request flow available under a JIRA issue and how it currently derives the title from the branch name. Define whether the issue title and key, and optionally a linked issue in the PR body, should be generated, then verify the resulting title and body through the GitHub-for-Jira integration flow.

Written by the indexing model from the issue text.