Feature: decision regulatory statement coupling

[elpoelma]

This PR includes a new in-app editor-plugin which allows users to insert regulatory statements in decisions. Specifically, the PR includes the following features:

• A modal which allows users to select and insert a regulatory statement in a decision.
• The regulatory statements are inserted as inline components in the editor document, they will always show the latest version of the included regulatory statement. The regulatory statements also have a static representation, which is an rdfa-annotated link to the linked regulatory statement container. The included regulatory statements are annotated with the https://data.vlaanderen.be/doc/applicatieprofiel/besluit-publicatie#Documentonderdeel type and dct:hasPart predicate.

TODO:

• Currently, a link between the regulatory statements and agendapoint document models is not stored yet. This PR includes commented code which allows storing such links, but we should further investigate how exactly we stored these links and if the relations should be many-to-many or one-to-many.
• Styling of the sidebar of the modal in which users can select regulatory statements.
• Addition of pagination to the modal
• At the moment it is still possible to include a regulatory statement twice in a document, this should probably be prevented.
• Investigate on how the publishing flow will work.

This PR is to be used in combination with lblod/ember-rdfa-editor#444 and lblod/app-gelinkt-notuleren#119

This PR is a solution to https://binnenland.atlassian.net/jira/software/c/projects/GN/boards/4?modal=detail&selectedIssue=GN-3725.