[plugin][refine-import] add configuration allowing refining into `Internal` namespace

[Anton-Latukha]

Feature request

Currently, the plugin requires people to manually refine imports if user wants to depend on Internal uncontrolled API.

#1832 (comment)

Solution

It should not be too hard to add the option into the plugin:
An example of Properties in type lenses plugin:

haskell-language-server/ghcide/src/Development/IDE/Plugin/TypeLenses.hs

Lines 89 to 112 in 7d7cfa2

	descriptor :: PluginId -> PluginDescriptor IdeState
	descriptor plId =
	(defaultPluginDescriptor plId)
	{ pluginHandlers = mkPluginHandler STextDocumentCodeLens codeLensProvider
	, pluginCommands = [PluginCommand (CommandId typeLensCommandId) "adds a signature" commandHandler]
	, pluginRules = rules
	, pluginConfigDescriptor = defaultConfigDescriptor {configCustomConfig = mkCustomConfig properties}
	}
	properties :: Properties '[ 'PropertyKey "mode" ('TEnum Mode)]
	properties = emptyProperties
	& defineEnumProperty #mode "Control how type lenses are shown"
	[ (Always, "Always displays type lenses of global bindings")
	, (Exported, "Only display type lenses of exported global bindings")
	, (Diagnostics, "Follows error messages produced by GHC about missing signatures")
	] Always
	codeLensProvider ::
	IdeState ->
	PluginId ->
	CodeLensParams ->
	LSP.LspM Config (Either ResponseError (List CodeLens))
	codeLensProvider ideState pId CodeLensParams{_textDocument = TextDocumentIdentifier uri} = do
	mode <- usePropertyLsp #mode pId properties

Alternatives solution

The current design can be seen as a good design, as it encourages best practices & discourages the use of uncontrolled Internal API: http://nikita-volkov.github.io/internal-convention-is-a-mistake.

But, still, people may have strong reasons & requirements to be able to refine into Internal modules when they need.