add cors headers to find interface

[willscott]

as you can see at https://cid.contact currently, query requests fail to load the json due to lack of cors cross-domain.

[codecov-commenter]

Codecov Report

Merging #252 (ad23756) into main (f44f8ea) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #252      +/-   ##
==========================================
+ Coverage   29.29%   29.34%   +0.04%     
==========================================
  Files          84       84              
  Lines       11851    11859       +8     
==========================================
+ Hits         3472     3480       +8     
  Misses       7880     7880              
  Partials      499      499              

Impacted Files	Coverage Δ
server/finder/http/server.go	87.50% <100.00%> (+2.50%)	⬆️

[gammazero]

In the future should we consider making the allowed origins configurable?

[willscott]

i think it's fine to leave that to an nginx layer rather than trying to have it be the indexer manage that complexity. i think the default is that anyone who can access the endpoint should be able to consume find requests browser or otherwise