This commit places the email CSS into the `style` tag located in the
`head` section. This resolves the issue of being unable to apply
certain CSS styles that cannot be inlined, such as media queries and
pseudo-classes.
In #23380 we want to change all ocurrences of `uri` to `url`. This
commit changes the ocurrences of `uri` appeared in files related to
email, including templates (`.html`, `.txt`) and backend (`.py`)
codes.
In `email.md`, `base_images_uri` is changed to `images_base_url` -
the words `base` and `images` are swapped and plural form is added
for `image`. This is becasue the former is not found anywhere in
the codebase while the later appears a lot. To reduce confusion,
this doccumentation changed accordingly.
The migration to css-inline "fixed" the fact that styles from this
file previously were never applied to the internals of missed-message
emails.
Rewrite much of the CSS to more correctly scope to apply to the
appropriate elements, and document with comments the purpose of most
blocks.
Co-authored-by: Tim Abbott <tabbott@zulip.com>
Previously, we had an architecture where CSS inlining for emails was
done at provision time in inline_email_css.py. This was necessary
because the library we were using for this, Premailer, was extremely
slow, and doing the inlining for every outgoing email would have been
prohibitively expensive.
Now that we've migrated to a more modern library that inlines the
small amount of CSS we have into emails nearly instantly, we are able
to remove the complex architecture built to work around Premailer
being slow and just do the CSS inlining as the final step in sending
each individual email.
This has several significant benefits:
* Removes a fiddly provisioning step that made the edit/refresh cycle
for modifying email templates confusing; there's no longer a CSS
inlining step that, if you forget to do it, results in your testing a
stale variant of the email templates.
* Fixes internationalization problems related to translators working
with pre-CSS-inlined emails, and then Django trying to apply the
translators to the post-CSS-inlined version.
* Makes the send_custom_email pipeline simpler and easier to improve.
Signed-off-by: Daniil Fadeev <fadeevd@zulip.com>
Daniil Fadeev
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