Resolve "Provide base templates for e-mails generated by apps"

Closes #439 (closed)

CHANGELOG.rst

@@ -20,6 +20,7 @@ Added
 * Views filtering for person names now also search the username of a linked user
 * OAuth2 applications now take an icon which is shown in the authorization progress.
 * Add support for hiding the main side nav in ``base.html``.
+* Provide base template and function for sending emails with a template.
 
 Fixed
 ~~~~~
@@ -51,6 +52,7 @@ Changed
   to authorize an external application.
 * Tables can be scrolled horizontally.
 * Overhauled person detail page
+* Use common base template for all emails.
 
 `2.5`_ – 2022-01-02
 -------------------