* adds model and form mixin for PIK
* integrates mixins for compensation, ema and ecoaccount
* adds migration files
* extends API
* extends API test data
* adds is_xy fields to compensation, ema and ecoaccount reports
* adds is_pik information to detail views
* adds/updates translations
* adds tests for team sharing
* extends the API for team sharing support
* adds shared_teams property shortcut for ShareableObjectMixin
* adds full support for team-based sharing to all views and functions
* simplifies ShareModalForm
* adds/updates translations
* adds team sharing field to share form
* splits sharing logic into user based and teams based
* adds TeamAdmin for admin backend
* adds validity check on Team name -> only unused names shall be valid
* adds creation tests with minimum data for intervention, compensation, ema and ecoaccount
* fixes bug where empty geometry would not be created properly using the API
* reworks key fetching from POST data, so inproperly stated keys will lead to an error for the API user, instead of silently working and use default data
* adds some logical checks for deductable_surface of eco account creation using api
* fixes bug that would have occured on creating compensations via api
* writes test for sharing using the API
* fixes bug on frontend form where an exception occured on generating a new API token if no token existed, yet
* adds permission constraint (default group) for using the api in general
* fixes default-group-only behaviour for sharing-API, so users can only add new users and not removing them, as long as they do not have any other group membership like registration or conservation office
* changes 'ksptoken' to 'Ksptoken' to match CGI standard for http header keys
