Define the on_stopped method in Puma::DSL

[OuYangJinTing]

Description

This is how it is described in README.md

However, using on_stopped in fact leads to an exception because the on_stopped method is not defined in Puma::DSL.

Your checklist for this pull request

• I have reviewed the guidelines for contributing to this repository.
• I have added (or updated) appropriate tests if this PR fixes a bug or adds a feature.
• My pull request is 100 lines added/removed or less so that it can be easily reviewed.
• If this PR doesn't need tests (docs change), I added [ci skip] to the title of the PR.
• If this closes any issues, I have added "Closes #issue" to the PR description or my commit messages.
• I have updated the documentation accordingly.
• All new and existing tests passed, including Rubocop.

PS: English is not my native language; please excuse typing errors.

Ref: #3379
Close #3380

[dentarg]

Can we add some test for this?

[OuYangJinTing]

Can we add some test for this?

✅

Please help me review it when you are free. Thank you.

[dentarg]

How it looks:

~/src/puma defined_on_stopped
$ echo 'app { [200, {}, ["OK"]] }; on_booted { puts "Hello World!" }; on_stopped { puts "Goodbye from hook" }' | b e ruby -Ilib bin/puma --config /dev/stdin --port 0 --log-requests
Puma starting in single mode...
* Puma version: 6.4.2 (ruby 3.2.4-p170) ("The Eagle of Durango")
*  Min threads: 0
*  Max threads: 5
*  Environment: development
*          PID: 11825
* Listening on http://0.0.0.0:61897
Use Ctrl-C to stop
Hello World!
^CGoodbye from hook
- Gracefully stopping, waiting for requests to finish
=== puma shutdown: 2024-06-15 20:56:43 +0200 ===
- Goodbye!

~/src/puma defined_on_stopped
$ echo 'app { [200, {}, ["OK"]] }; on_booted { puts "Hello World!" }; on_stopped { puts "Goodbye from hook" }' | b e ruby -Ilib bin/puma --config /dev/stdin --port 0 --log-requests --workers 2
[12253] Puma starting in cluster mode...
[12253] * Puma version: 6.4.2 (ruby 3.2.4-p170) ("The Eagle of Durango")
[12253] *  Min threads: 0
[12253] *  Max threads: 5
[12253] *  Environment: development
[12253] *   Master PID: 12253
[12253] *      Workers: 2
[12253] *     Restarts: (✔) hot (✔) phased
[12253] * Listening on http://0.0.0.0:61915
[12253] Use Ctrl-C to stop
[12253] - Worker 0 (PID: 12255) booted in 0.0s, phase: 0
[12253] - Worker 1 (PID: 12256) booted in 0.0s, phase: 0
Hello World!
^C[12253] - Gracefully shutting down workers...
Goodbye from hook
[12253] === puma shutdown: 2024-06-15 20:57:07 +0200 ===
[12253] - Goodbye!