Change how success is reported for the replication recovery API

Related to #235. This changes the how the recovery endpoint reports success. Instead of synchronously returning when recovery is successful, it will return success when the recovery attempt has begun. A separate endpoint will exist to allow the state to be polled.

Created by: codecov[bot]

Codecov Report

Merging #299 (92ea1e15) into main (302dba59) will increase coverage by 0.04%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #299      +/-   ##
==========================================
+ Coverage   91.44%   91.48%   +0.04%     
==========================================
  Files          51       51              
  Lines        4594     4594              
  Branches      631      631              
==========================================
+ Hits         4201     4203       +2     
+ Misses        343      342       -1     
+ Partials       50       49       -1     

Impacted Files	Coverage Δ
src/_zkapauthorizer/model.py	94.88% <0.00%> (+0.63%)

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Created by: hacklschorsch

Review: Approved

LGTM!