Add missing info for change column and table comment in Guides

[gustiando]

Summary

Some people (myself included) rely heavier on the guides for a quick reference more than the api docs. Thought I'd throw this one in there to see if it helps.

You can help improve the Rails guides or the API reference by making them more coherent, consistent, or readable, adding missing information, correcting factual errors, fixing typos, or bringing them up to date with the latest edge Rails.

This will address the "adding missing information" suggestion from the guide.

[jonathanhefner]

I think it makes sense to add these. Though it might be worth modifying "the change method supports only these migration definitions" to sound less final, in case of future missing entries like these.

When you are happy with the changes, would you mind squashing the commits?

[gustiando]

Thanks for the guidance @jonathanhefner . I'm happier with the changes now.

I was considering linking to the api docs or something. But am curious what you think. I tried to avoid blowing up the scope of this change too much. Happy to accommodate if you have better suggestions though :)

[jonathanhefner]

I was considering linking to the api docs or something. But am curious what you think. I tried to avoid blowing up the scope of this change too much.

Do you mean adding another link, in addition to the individual method links? I think it would be nice to do so, but there doesn't seem to be a definitive place to link to. Linking to SchemaStatements for its list of methods doesn't seem quite right because there are additional methods listed there. Adding some documentation to the SchemaStatements module itself might improve that, but, I agree, that would be out of scope for this PR.

[gustiando]

Do you mean adding another link, in addition to the individual method links?

@jonathanhefner yes, that's what I had in mind.

[jonathanhefner]

Thank you, @gumatias! 🎉

Backported to 7-0-stable in 05e1f70.