hpack handler for cabal-install

[l29ah]

It would be nice if cabal-install could detect a hpack package description file being present and called hpack in such cases, when it doesn't see a .cabal in the directory.

[jneira]

@I29ah Hi, thanks for your feature proposal, the inclusion of hpack was discussed in depth in this issue: #5343 as one of the hpack features wanted in cabal is the automatic module discovering.
Iiuc in that issue was mentioned that a possible solution could be add some sort of generic "preprocessor" support which could be used with hpack (or other preprocessor like dhall-to-cabal f.e.)