Redirect to @record or path in controller generator

[jeromedalbert]

Partially addresses rails/rails#52756

Problem

There is some discrepancy between Rails controller generators and jbuilder controller generators when it comes to redirects.

Solution

This PR changes the controller generator to generate redirects with redirect_to @post or _path, in order to match the Rails codebase generators as close as possible.

[jeromedalbert]

Tests fail for Rails 5 because singular_route_name is not available in that version. I am wondering if a better fix would be to stop testing against Ruby version 2.7 and Rails 5 since both version are end of life. If so I can update this PR or make a separate one.

[skipkayhil]

Would redirect_to @post work in this case? I think that's what the Rails' templates are generating now (however, redirect_to @post is still redirecting with a full URL which maybe(?) DHH is wanting to change)

[dhh]

Yes, let's change to redirect_to @post so it matches the generator in Rails itself. They should be as close as possible.

[jeromedalbert]

PR updated. Tests are failing for Rails 5.0 and 5.1 because redirect_resource_name looks like it was added in Rails 5.2.

I would suggest not testing against these end of life versions any more. Here is a PR to do so: #570.