Provide single admin interface for the integration regex customization

Problem Definition

According to BSERV-2470 Bitbucket Server does not verify if the JIRA issue actually exists. However different integration options are difficult to configure or even hardcoded:

• integration.jira.key.pattern is responsible for setting the patter for the JIRA issue key detection in the commit comments or pull requests
• issueKeyRegex is hardcoded regex into pull request from which remove the punctuation from the pull request title if the branch name contain underscore or other punctuation in the name while preserving the JIRA issues keys

As JIRA project key can contain underscores as mentioned in Changing the project key format it can lead to incorrect issue detection so that requeres the customization of the default regexes.

Suggested Solution

Provide the single configuration interface for such changes to provide simple and convenient way to provide compatibility with all the possible JIRA project ID.

Why this is important

While the default settings are causing end users frustration because of incorrect statistics on JIRA tickets the customization of the regexes in a different part of the systems are increasing the upgrade complexity for the system administrators.