caching and cookie management

[fisx]

1. i experienced weird behavior that could only be fixed by deleting all cookies, and i turned out to have collected a lot of them.
2. we have not thought about caching at all so far. there may be some performance to be gained, especially if we use some hashing-naming-scheme for the /static content, but there may also be some hidden issues with stale pages that are delivered from cache, but shouldn't.

[fisx]

related, or duplicate of: #283.

[fisx]

Link „Profil anzeigen“ in user menu in main nav redirects to idea space overview
https://aula-stage1.liqd.net/user/18/ideas

moritz, can you clear all you aula-related cookies and try to reproduce this?
i suspect it won't work. this is a known bug.
Moritz: Link worked as expected again, when I tested it this morning

[fisx]

this may be resolved by now. not sure, though.

[fisx]

lots of packages on hackage:

• http://hackage.haskell.org/package/wai-middleware-preprocessor
  more for compiling purescript dynamically on delivery
• http://hackage.haskell.org/package/wai-middleware-etag
  almost what we want, but doesn't watch file changes
• http://hackage.haskell.org/package/wai-middleware-static-caching
  probably good for inspiration, but doesn't help with cache busting.
• http://hackage.haskell.org/package/wai-middleware-caching
  only server-side
• http://hackage.haskell.org/package/wai-static-cache
  only server-side
• http://hackage.haskell.org/package/wai-middleware-cache
  only server-side

nothing that does browser cache busting.

[fisx]

goal:

• cache everything under /static
• do not cache anything else
• every reference to a cached resource should end with [?|&]last_changed=<epoch_time>

we could write a more sophisticated (and much slower) middleware that parses all of html, css, js, and whatever else i forgot, but...

[fisx]

This has been resolved in #735.

(I opened #921 to keep the last two comments in scope.)