Enhance formatting of the cabal-version error message (haskell#4436)

* Fix formatting of the `cabal-version` error message

Add docs for `cabal-add` based CodeAction

* Apply suggestions from code review

Co-authored-by: VeryMilkyJoe <jana.chadt@nets.at>

---------

Co-authored-by: VeryMilkyJoe <jana.chadt@nets.at>

Author: fendor

docs/features.md

@@ -316,6 +316,14 @@ Code action kind: `quickfix`
 
 Correct common misspelling of SPDX Licenses such as `BSD-3-Clause`.
 
+### Add dependency to `cabal` file
+
+Provided by: `hls-cabal-plugin`
+
+Code action kind: `quickfix`
+
+Add a missing package dependency to your `.cabal` file.
+
 ## Code lenses
 
 ### Add type signature

plugins/hls-cabal-plugin/src/Ide/Plugin/Cabal.hs

@@ -254,8 +254,10 @@ cabalRules recorder plId = do
                 -- user did not do anything wrong. Instead we cast it to a warning
                 regex = "Unsupported cabal-version [0-9]+.[0-9]*"
                 unsupportedCabalHelpText = unlines
-                  [ "The used cabal version is not fully supported by HLS. This means that some functionality might not work as expected."
-                  , "If you face any issues try to downgrade to a supported cabal version."
+                  [ "The used `cabal-version` is not fully supported by this `HLS` binary."
+                  , "Either the `cabal-version` is unknown, or too new for this executable."
+                  , "This means that some functionality might not work as expected."
+                  , "If you face any issues, try downgrading to a supported `cabal-version` or upgrading `HLS` if possible."
                   , ""
                   , "Supported versions are: " <>
                       List.intercalate ", "