Introduce suspenders:migrate task

Lifted from our [dotfiles][], this task runs the latest migration, rolls
it back, and runs it again in an effort to ensure it's reversible. More
context can be found [in these comments][].

Unfortunately, this implementation did not work because Rake recognized
that it `db:migrate` was already invoked, so it wasn't invoked a second
time. Instead, we needed to `reenable` the task manually.

```ruby
task migrate: ["db:migrate", "db:rollback", "db:migrate", "db:test:prepare"]
```

[dotfiles]: https://github.com/thoughtbot/dotfiles/blob/f149484269ef98e2bc80b7daa1988e214ddf8e8b/aliases#L12
[in these comments]: thoughtbot/dotfiles@4882c41#r1933964

NEWS.md

@@ -12,6 +12,7 @@ Unreleased
 * Introduce `suspenders:views` generator
 * Introduce `suspenders:setup` generator
 * Introduce `suspenders:tasks` generator
+* Introduce `suspenders:migrate` task
 
 20230113.0 (January, 13, 2023)
 

README.md

@@ -150,6 +150,15 @@ Creates local Rake tasks for development
 bin/rails dev:prime
 ```
 
+#### Suspenders Tasks
+
+Custom Suspenders tasks
+
+```
+bin/rails suspenders:rake
+bin/rails suspenders:migrate
+```
+
 ## Contributing
 
 See the [CONTRIBUTING] document.

lib/tasks/suspenders.rake

@@ -9,4 +9,15 @@ namespace :suspenders do
       Rake::Task[:standard].invoke
     end
   end
+
+  desc "Ensure a migration is reversible"
+  task :migrate do
+    Rake::Task["db:migrate"].invoke
+    Rake::Task["db:rollback"].invoke
+
+    Rake::Task["db:migrate"].reenable
+    Rake::Task["db:migrate"].invoke
+
+    Rake::Task["db:test:prepare"].invoke
+  end
 end