*: website_appointment__account_payment, website_enterprise

In order to easily display existing appointments on the website, add an 'Appointments'
dynamic snippet. It will display punctual and recurring appointments, published and
linked to the current website (or all).

Also, a few options are added:
- One can filter on Users / Resources
- If one of those is used, the user can select existing users / resources to
filter the displayed appointments
- Also, one can specify a list of comma separated names that will be used to
search appointments based on 'name'.

Some placeholder data is added. The snippet template is the same one as appointment
cards on the front-end. Therefore, the card template has been split into sub
templates, being called in the snippet one. The split is done in a separate commit.
The main difference is the display of the sample ribbon.

The previous 'Appointment' snippet, which adds a button that can redirect to
appointments (with some options) is renamed (in strings, not in the files, to avoid
versioning the snippet) to 'Appointment Button' to be more explicit.

In a separate commit, align domains used to fetch and choose appointment types for
the s_online_appointment snippet. (including both website and datetime domains)

Task-3889948