Adding specs for the has_key_for? method

[jwoertink]

Purpose

This is to accompany luckyframework/avram#500

Description

This adds in specs for the new params.has_key_for? method. Though the method is defined in Avram, we can't accurately write specs for it in Avram since a user's params will actually be Lucky::Params. In this case, it's closer to "real world" tests.

Checklist

• - An issue already exists detailing the issue/or feature request that this PR fixes
• - All specs are formatted with crystal tool format spec src
• - Inline documentation has been added and/or updated
• - Lucky builds on docker with ./script/setup
• - All builds and specs pass on docker with ./script/test

[paulcsmith]

IMO I think we should remove this from Lucky and keep it in Avram. Right now we could change has_key_for? to anything we want in Avram and we wouldn't know if it works or is broken until we pull master into Lucky and run the specs here. I think since the logic is in Avram the spec should be there. I left an example here: luckyframework/avram#500 (comment) of how it could be done