Fs cloning api route

[mpacer]

This builds on #163 (and so should be reviewed in contrast to it rather than in its entirety).

This enables end-to-end testing of the full file system cloning experience.

[codecov[bot]]

Codecov Report

Merging #164 into master will decrease coverage by 1.11%. The diff coverage is 68.29%.

@@            Coverage Diff             @@
##           master     #164      +/-   ##
==========================================
- Coverage   81.15%   80.03%   -1.12%     
==========================================
  Files          10       10              
  Lines         467      506      +39     
==========================================
+ Hits          379      405      +26     
- Misses         88      101      +13

[codecov[bot]]

Codecov Report

Merging #164 into master will increase coverage by 0.03%. The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #164      +/-   ##
=========================================
+ Coverage   82.57%   82.6%   +0.03%     
=========================================
  Files          10      10              
  Lines         505     506       +1     
=========================================
+ Hits          417     418       +1     
  Misses         88      88