This marks the function safe and returns Result, it also now returns
the ConfiguredAddr since it has to look this up anyway and it makes
testing more easy. Turns out it reduces some duplicate SQL query in
some callers too.
More test code has been moved from dc_imex to test_utils as it's
more genrally applicable.
* refactor(contact): rename and rusty memory allocations
* refactor(contact): use enum to indidcate origin
* refactor(contact): safe blocking and unblocking api
* refactor(contact): only safe and no more cstrings