DATABASE option for railties:install:migrations

[SixiS]

Motivation / Background

This Pull Request has been created because it is helpful to be able to specify which database you want
to install migrations to when using an engine with a Rails project that has multiple databases.

Detail

This Pull Request adds a DATABASE option to the railties:install:migrations rake task.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Changes that are unrelated should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[rafaelfranca]

Suggested change

	destination = ActiveRecord::Tasks::DatabaseTasks.migrations_paths.first
	if ENV["DATABASE"].present? && ENV["DATABASE"] != "primary"
	config = ActiveRecord::Base.configurations.configs_for(name: ENV["DATABASE"])
	raise "Invalid DATABASE provided" if config.blank?
	destination = config.migrations_paths
	raise "#{ENV["DATABASE"]} does not have a custom migration path" if destination.blank?
	end
	if ENV["DATABASE"].present? && ENV["DATABASE"] != "primary"
	config = ActiveRecord::Base.configurations.configs_for(name: ENV["DATABASE"])
	raise "Invalid DATABASE provided" if config.blank?
	destination = config.migrations_paths
	raise "#{ENV["DATABASE"]} does not have a custom migration path" if destination.blank?
	else
	destination = ActiveRecord::Tasks::DatabaseTasks.migrations_paths.first
	end