Notes on Page.send_page and the like

Page.send_page gets called from many locations in the code. To factor out the code into reusable parts i will keep an overview over common flows through it's code here. I take on the actions first, beginning every entry with a table of used parameters and where they originate from in this context.

Action 'show' (default action)

1. 'VIEWPAGE' is logged to the eventlog
2. handle 'redirect'

   1. no explicit 'show' action and not already redirected? => http-redirect, END HERE

3. instantiate 'text/html' formatter
4. replace request.formatter, remember old
5. handle 'deprecated'
   1. add deprecation message
   2. append old page-body to current
6. set the content language for the request
7. set http cache headers
8. emit headers
9. handle (old) revision requested
   1. add message with revision info
10. handle 'redirect' (again!)
    1. if has been redirected, set redirected-from message
    2. if is redirecting page, set redirects-to message
11. get user-trail
12. send theme title
13. handle several cases mutually exclusive
    1. handle page not exist

       1. get MissingPage/MissingHomePage

       2. call .send_page recursively (content_only=1, send_missing_page=1)
    2. handle user-ACL mismatch
       1. just emit a "you are not allowed ..." message
    3. standard case (existant page, matching ACLs)
       1. output page content via formatter
       2. emit footnotes
14. send theme footer
15. send theme closing html
16. handle page exist
    1. create pagelinks cache
17. restore request.formatter