[tests] Test timestamp formats that include timezones
[tests] Fix typo in common tests
[common] Fix typo in exception message

Unit tests updated acording to the changed made.
[Redmine] Add RedmineIssue class

Unit tests updated.
[Redmine] Include attachments param in issue details URL
[Redmine] Add RedmineAttachment class

Unit tests updated.
[Redmine] Include relations param in issue details URL
[Redmine] Issue parser for Redmine backend
[tests] Unit tests for Redmine issue parser