provide more control over formatting.

ada_language_server uses the gnatpp code to do formatting. That code supports several options that control the formatting. In particular, some combination of settings results in "just indent", which is what Emacs ada-mode wants when the user invokes indent-line.

So it would be nice if there was a way to pass those options to the server, perhaps via an LSP extension command ada_format_options.

In addition, the gnatpp code has a set of formatting rules that can be specified in a file (at least, it did last time I looked; it seems that feature was only intended for internal development). It would be nice to allow the user to specify a file to replace the formatting rules; then we could implement any formatting style using ada_language_server.