`.env.public` approach to `Makefile` variables: quotes are literal in GNU Make

[zmughal]

If the .env.public file is meant to be used as both a source-able .env file and as Makefile variables, it must use the intersection of their syntaxes which is stricter on special characters. For GNU Make, this means that any quotes (m/["']/) will be literal quotes in the GNU Make variable, but sh(1) will use the contents of the quoted string.

It might be better to treat it as just Makefile variables (e.g., config.Makefile) and apply the appropriate quoting in the GNU Make recipe commands.

Full details mentioned here: #95 (comment) (with a patch I do not like).

[noelmcloughlin]

Hi @zmughal Sorry for delay. I think we could just do a PR to remove quotes from https://github.com/linkml/linkml-project-cookiecutter/blob/main/%7B%7Bcookiecutter.project_name%7D%7D/.env.public
They are not necessary for source-able .env file

[zmughal]

I believe that this can be closed via #123.