fix: allow commas in email confirmation sender

[mantariksh]

Problem

We allow admins to specify the email sender for email confirmations. However, when the sender contains a comma, the text before the comma gets cut off.

Example from production

Specifying an email sender with a comma

Actual email sender

Solution

According to this issue, sender names containing commas must be wrapped in quotes. This fixed the problem.

Example from staging

Specifying an email sender with a comma

Actual email sender

Backwards compatibility

Note that for senders without special characters, the email headers actually remain unchanged, so this change is backwards compatible even for receivers which are manually parsing email headers. For senders with special characters, the email headers get fixed by the inclusion of quotes.

Without comma, before (production)

Without comma, after (staging)

With comma, before (production)

With comma, after (staging)

Tests

• Add an email field with email confirmation. Add a sender string with a comma in it and submit the form. Check that the sender string appears correctly in your email.

[karrui]

lgtm