FIX: migrations-tooling CLI didn't work anymore (#29777)

The previous approach of splitting Thor commands into multiple files caused problems when the same method name was used in multiple commands.

This also loads the Rails environment only for commands that need it. That makes the CLI boot faster for most commands or when the help should be shown. That's also why we can't use `Rails.root` in the CLI.

migrations/lib/cli/convert_command.rb

@@ -1,52 +1,48 @@
 # frozen_string_literal: true
 
-module Migrations::CLI::ConvertCommand
-  def self.included(thor)
-    thor.class_eval do
-      desc "convert [FROM]", "Convert a file"
-      option :settings, type: :string, desc: "Path of settings file", banner: "path"
-      option :reset, type: :boolean, desc: "Reset database before converting data"
-      def convert(converter_type)
-        converter_type = converter_type.downcase
-        validate_converter_type!(converter_type)
+module Migrations::CLI
+  class ConvertCommand
+    def initialize(converter_type, options)
+      @converter_type = converter_type.downcase
+      @options = options
+    end
 
-        settings = load_settings(converter_type)
+    def execute
+      validate_converter_type!
+      settings = load_settings
 
-        ::Migrations::Database.reset!(settings[:intermediate_db][:path]) if options[:reset]
+      ::Migrations::Database.reset!(settings[:intermediate_db][:path]) if @options[:reset]
 
-        converter = "migrations/converters/#{converter_type}/converter".camelize.constantize
-        converter.new(settings).run
-      end
+      converter = "migrations/converters/#{@converter_type}/converter".camelize.constantize
+      converter.new(settings).run
+    end
 
-      private
+    private
 
-      def validate_converter_type!(type)
-        converter_names = ::Migrations::Converters.names
+    def validate_converter_type!
+      converter_names = ::Migrations::Converters.names
 
-        raise Thor::Error, <<~MSG if !converter_names.include?(type)
-            Unknown converter name: #{type}
-            Valid names are: #{converter_names.join(", ")}
-          MSG
-      end
+      raise Thor::Error, <<~MSG if !converter_names.include?(@converter_type)
+        Unknown converter name: #{@converter_type}
+        Valid names are: #{converter_names.join(", ")}
+      MSG
+    end
 
-      def validate_settings_path!(settings_path)
-        if !File.exist?(settings_path)
-          raise Thor::Error, "Settings file not found: #{settings_path}"
-        end
-      end
+    def validate_settings_path!(settings_path)
+      raise Thor::Error, "Settings file not found: #{settings_path}" if !File.exist?(settings_path)
+    end
 
-      def load_settings(converter_type)
-        settings_path = calculate_settings_path(converter_type)
-        validate_settings_path!(settings_path)
+    def load_settings
+      settings_path = calculate_settings_path
+      validate_settings_path!(settings_path)
 
-        YAML.safe_load(File.read(settings_path), symbolize_names: true)
-      end
+      YAML.safe_load(File.read(settings_path), symbolize_names: true)
+    end
 
-      def calculate_settings_path(converter_type)
-        settings_path =
-          options[:settings] || ::Migrations::Converters.default_settings_path(converter_type)
-        File.expand_path(settings_path, Dir.pwd)
-      end
+    def calculate_settings_path
+      settings_path =
+        @options[:settings] || ::Migrations::Converters.default_settings_path(@converter_type)
+      File.expand_path(settings_path, Dir.pwd)
     end
   end
 end