1. Improve ConfluenceMediaFetcher

ovh.atlasinc.ap.web.dashboard.renderers.page.ConfluenceMediaFetcher#queryContent
if two threads call this function at approximately the same time, fetchMediaIdsMapping(docId) will be called twice, because until the first CompletableFuture completes, there is no docId in queriedDocIds.

example:
ovh.atlasinc.jira_issue_html_renderer.JiraAdfToHtmlComparingMediaFetcher#supplyMapping(ovh.atlasinc.connect.jira.Issue)

the second thing is that the docId is unique only in a given space, so when there are e.g. /include to other spaces, it may be repeated
example new default media fetcher for confluence:
https://bitbucket.org/warsawdynamics/atlassian/src/ea6ab9ed8beb616b3af0f04dc80b88859853e9c0/confluence-page-html-renderer/src/main/java/ovh/atlasinc/confluence_page_html_renderer/ConfluenceMediaFetcher.java?at=PEFC-3-Create_application

1. Also we could work on issue fields support for external user in APFJ since they are now available in PDF Export.

Since there were no problems with external approver confluence page preview, im leaving this task for now.