Add support for text columns for secure matchers

[maxehmookau]

Issue

Currently, using the text datatype for the has_secure_token functionality is supported in Rails, but when used alongside shoulda-matchers it fails as the datatype must be string.

On codebases that use postgresql, there's no difference between using text or string and in most cases it makes sense to use text.

Proposed solution

Add support for text datatypes when using the have_secure_token matcher.

[maxehmookau]

I'm really struggling to get appraisals working to run the specs locally so I'm not convinced this works yet. 😢

[krainboltgreene]

Mind if I copy this PR with the requested changes so we can get this merged in?

[matsales28]

@krainboltgreene, sorry for the delayed response. I wasn't following this PR.

I'd say to feel free to copy this PR with the requested changes just make sure to also give credits to @maxehmookau