Improve restricted access screen for Unlicensed/Anonymous

Issue Summary

This is reproducible on Data Center:  (no)

When a user is unaware they are browsing either unlicensed or anonymously and they attempt to access content open only to licensed users, they get a generic "You've stumbled onto restricted space/page" messaging. This results in confusion from users, who reach out to IT to help resolve their access problem. 

Steps to Reproduce

As an anonymous user, there are multiple scenarios which can cause this behavior such as being unaware of

• expired session with browser tabs open after extended time away (eg PTO)
• browsing incognito
• browsing in a new browser without authenticating to confluence

When a confluence site also has unlicensed access enabled for JSM knowledge base, some example scenarios include

• expired session (as above)
• existing Atlassian user who was just issued a Confluence license (expected delay for license data to propogate across internal systems)

Expected Results

• Communicate to the user when attempting to access as either an anonymous or unlicensed user
• Provide options to log in or (if applicable) step into the request license access flow

Actual Results

"You’ve stumbled onto a restricted space" message"

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available