Add Discoverable and Source to Account & add ability to get pinned posts

[codecov-commenter]

Codecov Report

Merging #147 (01a4ad5) into master (87278bd) will increase coverage by 0.09%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #147      +/-   ##
==========================================
+ Coverage   79.69%   79.79%   +0.09%     
==========================================
  Files          31       31              
  Lines        1438     1445       +7     
==========================================
+ Hits         1146     1153       +7     
  Misses        201      201              
  Partials       91       91              

Impacted Files	Coverage Δ
accounts.go	100.00% <100.00%> (ø)

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[RasmusLindroth]

Also add support for pinned posts

[mattn]

Thank you