fix(Public-Sharing): Show footer with server details and eventual ToS through...

fix(Public-Sharing): Show footer with server details and eventual ToS through PublicTemplateResponse

The public calendar view used 'base' Template responses, preventing the footer that's being used on other public sharing pages from showing. This makes use of PublicTemplateResponse to show it automatically. It's however hidden on embed view.

Reference: https://help.nextcloud.com/t/feature-request-impressum-and-privacy-declaration-links/161162


Signed-off-by: Thomas Citharel <tcit@tcit.fr>