CustomizeConnection::on_release()

[djc]

@agersant how do you feel about this?

[codecov]

Codecov Report

Merging #94 (56ef326) into main (50e7e4f) will increase coverage by 1.41%.
The diff coverage is 93.75%.

@@            Coverage Diff             @@
##             main      #94      +/-   ##
==========================================
+ Coverage   80.38%   81.80%   +1.41%     
==========================================
  Files           6        6              
  Lines         668      720      +52     
==========================================
+ Hits          537      589      +52     
  Misses        131      131              

Impacted Files	Coverage Δ
bb8/src/inner.rs	83.84% <81.25%> (+2.17%)	⬆️
bb8/src/api.rs	66.31% <83.33%> (-0.71%)	⬇️
bb8/src/internals.rs	92.40% <100.00%> (ø)
bb8/tests/test.rs	87.75% <100.00%> (+1.43%)	⬆️

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[agersant]

Looks good to me, thanks for following up on this!

[djc]

I ended up removing it before release, since I'm not confident in the mechanics (I found at least one gap which wasn't that easy/clean to solve), and I can't really think of a use case. Will leave this out for now and add it back if someone comes up with a use case.

[paolobarbolini]

This is exactly what we need for lettre. We have a PR lettre/lettre#550 for adding a connection pool to our async version of the API, but we need a way for quit to be called before dropping a connection. on_release would be perfect for this. It's also what we use in the sync version of our API, based on r2d2

[djc]

Can you open a new issue and preferably a PR?