IGAPP-296: Use category/event/poi metadescriptions from cms

[jira-to-github-migrator-test]

Steffen Kleinle - 7.10.2020, 15:26:04

As a (google) search engine user I want to see good meta descriptions so that I want to click on the search result and open Integreat. These meta descriptions should be configurable per category.

Acceptance Criteria (Successes/Failures):

• Meta descriptions for categories/events/pois from the cms are used
• If no custom meta description is available from the cms, the default google text should be shown (no action required from our side)

Corresponding cms issue: digitalfabrik/integreat-cms#522

Environment: -
Linked issues:

• Issue split: IGAPP-1195
• Relates: IGAPP-295