Implement Party map caching

[M4LuZ]

Expected Behavior

Map is only regenerated if attendee list changes. Optionally also when user edits his postcode.

Current Behavior

Every map access recalcutes map positions.
Implementation is client-wise instead of on the server.
This makes queries (and in case of google cost) increment lineary

Possible Solution

• Query geolocation service on server (e.g. https://developers.google.com/maps/documentation/javascript/mysql-to-maps )
• Store results with mapping to postcode in cache / DB
• Draw from stored results
• Trigger update when user is set to paid / registered / unpaid / unregistered. So whenever also the party attendee statistics are updated.
• Additionally the map would also need a redraw if user changes his postcode

Context

This causes the usermap both to be slow and may even cause costs. Thus should be optimized

Your Environment

• Version used: Git/Master/HEAD
• Operating System and version: Any
• Enabled features: Usermap