[Elm] Description conversion to function comment can be improved

[andys8]

Description

Comments describing a function or declaration start with {-| instead of {-. They belong to the next declaration.

{-| Representation of fast immutable arrays. You can create arrays of integers
(`Array Int`) or strings (`Array String`) or any other type of value you can
dream up.
-}
type Array a = Array

https://github.com/elm-lang/core/blob/5.1.1/src/Array.elm#L39-L43

The codegen will generate this (including newlines) instead (the | character is missing):

{-
   My description
-}

and if there is no description at all, the output will be a comment with no content. Instead the comment should be omitted.

{-

-}

Swagger-codegen version

2.3.1

Suggest a fix/enhancement

The parentheses are hardcoded. There could be more occurrences.

swagger-codegen/modules/swagger-codegen/src/main/resources/elm/model.mustache

Lines 14 to 16 in d6539ba

	{-
	{{{description}}}
	-}

swagger-codegen/modules/swagger-codegen/src/main/resources/elm/api.mustache

Lines 16 to 18 in d6539ba

	{-
	{{notes}}
	-}