Create a shape validation service

In some cases, especially when working with external data, validating data will become easier and more reliable when validating data at the beginning of a transaction once and then being able to rely on the validation.

In addition to using the shapes for typing support, we can use them to validate (or filter) incoming data.

This includes
- A new service with actions to validate data against a certain shape
- A moleculer mixin for controlled containers which you can use to constrain the shape of a given LDP container
- A [custom validator](https://moleculer.services/docs/0.14/validating#Custom-validator) for Moleculer which you can use to specify the required shape of parameters?

The issue names no files, tests, or entry points. Start by locating the existing shape definitions and Moleculer service and mixin structure, then clarify the boundaries of the validation service, controlled-container mixin, and custom validator. Done requires an agreed scope and working coverage for the selected components.

Written by the indexing model from the issue text.