Specialize Rails7 Database setup

In Rails 6.1 the tasks used for database setup in our test pack were deprecated. They were removed in Rails 7 https://edgeguides.rubyonrails.org/7_0_release_notes.html.

This commit moves to specialize the tasks for Rails7+ to use `db:schema:load` per deprecation instruction:

```
DEPRECATION WARNING: Using `bin/rails db:schema:load_if_ruby` is deprecated and will be removed in Rails 7.0. Configure the format using `config.active_record.schema_format = :ruby` to use `schema.rb` and run `bin/rails db:schema:load` instead. (called from <main> at /app/bin/rake:4)
```

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Main (unreleased)
 
+* Fix deprecated rake tasks for Rails 7 on Heroku CI (https://github.com/heroku/heroku-buildpack-ruby/pull/1257)
+
 ## v235 (2022/01/03)
 
 * Bundler 2.x is now 2.2.33 (https://github.com/heroku/heroku-buildpack-ruby/pull/1248)

lib/language_pack/test.rb

@@ -3,5 +3,8 @@
 module LanguagePack::Test
 end
 
+# Behavior changes for the test pack work by opening existing language_pack
+# classes and over-writing their behavior to extend test functionality
 require "language_pack/test/ruby"
 require "language_pack/test/rails2"
+require "language_pack/test/rails7"

lib/language_pack/test/rails2.rb

@@ -1,4 +1,5 @@
-#module LanguagePack::Test::Rails2
+# Opens up the class of the Rails2 language pack and
+# overwrites methods defined in `language_pack/test/ruby.rb`
 class LanguagePack::Rails2
   # sets up the profile.d script for this buildpack
   def setup_profiled(ruby_layer_path: , gem_layer_path: )
@@ -51,7 +52,6 @@ def clear_db_test_tasks
     end
   end
 
-  private
   def db_prepare_test_rake_tasks
     schema_load    = rake.task("db:schema:load_if_ruby")
     structure_load = rake.task("db:structure:load_if_sql")

lib/language_pack/test/rails7.rb

@@ -0,0 +1,9 @@
+# Opens up the class of the Rails7 language pack and
+# overwrites methods defined in `language_pack/test/ruby.rb` or `language_pack/test/rails2.rb`
+class LanguagePack::Rails7
+  # Rails removed the db:schema:load_if_ruby and `db:structure:load_if_sql` tasks
+  # they've been replaced by `db:schema:load` instead
+  def db_prepare_test_rake_tasks
+    ["db:schema:load", "db:migrate"].map {|name| rake.task(name) }
+  end
+end

lib/language_pack/test/ruby.rb

@@ -1,4 +1,8 @@
-#module LanguagePack::Test::Ruby
+# Opens up the class of the Ruby language pack and
+# overwrites methods defined in `language_pack/ruby.rb`
+#
+# Other "test packs" futher extend this behavior by hooking into
+# methods or over writing methods defined here.
 class LanguagePack::Ruby
   def compile
     new_app?
@@ -26,7 +30,6 @@ def compile
     super
   end
 
-  private
   def db_prepare_test_rake_tasks
     ["db:schema:load", "db:migrate"].map {|name| rake.task(name) }
   end