[12.0][IMP] connector_jira: improved user binding

[alexey-pelykh]

• specify key/value when user binding fails
• resolve by login (which is unique) first, then my potentially-conflicting email
• if multiple JIRA users are returned, merge them by key as it's unique

@guewen @simahawk please review

[pedrobaeza]

/ocabot merge patch

[OCA-git-bot]

On my way to merge this fine PR! Rebased to 12.0-ocabot-merge-pr-8-by-pedrobaeza-bump-patch, awaiting test results.

[OCA-git-bot]

Congratulations, your PR was merged at 3dc3e947e09646fb2ba73993842336730db235d0. Thanks a lot for contributing to OCA. ❤️

PS: Don't worry if GitHub says there are unmerged commits: it is due to a rebase before merge. All commits of this PR have been merged into 12.0.