Dry-schema integration

[waiting-for-dev]

Integration with dry-schema validation library.

This extension provides a simple integration with dry-schema
library to streamline param sanitization.

On its own, the library just provides with a
Conn#sanitized_params method, which will return what is set into
bag's :sanitized_params key.

This key in the bag is what will be populated by SanitizeParams
plug, which accepts a dry-validation schema that will be applied
to Conn#params:

require 'web_pipe'

WebPipe.load_extensions(:dry_schema)

class App
  include WebPipe

  Schema = Dry::Schema.Params do
    required(:name).filled(:string)
  end

  plug :sanitize_params, WebPipe::Plugs::SanitizeParams[Schema]
  plug(:do_something_with_params) do |conn|
    DB.persist(:entity, conn.sanitized_params)
  end
end

By default, when the result of applying the schema is a failure,
Conn is tainted with a 500 as status code. However, you can
specify your own handler for the unhappy path. It will take the
Conn and Dry::Schema::Result instances as arguments:

plug :sanitize_params, WebPipe::Plugs::SanitizeParams[
                           Schema,
                           ->(conn, result) { ... }
                         ]

A common workflow is applying the same handler for all param
sanitization across your application. This can be achieved setting
a :param_sanitization_handler bag key in a upstream operation
which can be composed downstream for any number of
pipes. SanitizeParams will used configured handler if none is
injected as argument. Another plug ParamSanitizationHandler
exists to help with this process:

class App
  plug :sanitization_handler, WebPipe::Plugs::ParamSanitizationHandler[
                                ->(conn, result) { ... }
                              ]
end

class Subapp
  Schema = Dry::Schema.Params { ... }

  plug :app, App.new
  plug :sanitize_params, WebPipe::Plugs::SanitizeParams[Schema]
end