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.
Making sender name go in-line with message body only if
the html starts with <p> tag since it won't look good
if the message starts with a code snippet, ul, etc.
If message starts with p tag we can safely assume that
it can go in-line with sender name.
Make sure 's, &s, and other characters are not HTML-escaped in subject
lines and plain-text emails.
Hack so that this isn't blocking the release of Zulip 1.6. A more robust way
to do this would be to have two different template Engines, one that renders
HTML, and one that doesn't.
Fixes#5088.