Fix hlint warnings for hlint v2.1.20 (#1320)

* Apply some hlint suggestions.

* Simplify config parser (to avoid hlint error)

* Reorganize for clarity (and fix hlint error)

* Remove redundant language extension

* Reformat slice more conventionally to avoid hlint bug

* Refactor for clarity (and to avoid hlint error)

* Simplify (and avoid hlint error)

* Fix hlint complaint

test/Main.hs

@@ -55,7 +55,7 @@ main = do
     ver <- getPgVersion
     HT.transaction HT.ReadCommitted HT.Read $ getDbStructure "test" ver
 
-  dbStructure <- pure $ either (panic.show) id result
+  let dbStructure = either (panic.show) id result
 
   getTime <- mkAutoUpdate defaultUpdateSettings { updateAction = getCurrentTime }