refactor RSS consumption to use the JiraIssueResolver class

[pmauduit]

Now that the work of getting rid of the JIRA API client has been done, I realize that the RSS calls could be managed by the JiraIssueResolver class as well.

And at the end, the class handles much more than just the necessary calls for the "issue resolving" process, so maybe renaming it JiraConfluenceApi and/or separate the issue resolving into another class ?