fix: persist delivered email body in MemberEmailDelivery - #2827

Problem

member_email_deliveries.body has never captured any content — all 439 rows in production are empty, so the email audit log cannot show what was actually sent.

Root cause

premailer-rails registers a Mail interceptor that runs during delivery: it converts the message to multipart/alternative (adding a plain-text part and inlining CSS), which empties the body container. EmailDelivery#log_sent_email then runs in an after_deliver callback and reads mail.body.to_s — the now-empty container — storing "".

The emails themselves are unaffected: recipients receive complete multipart/alternative messages with both plain-text and HTML parts. Only the audit log is broken. Chaser dedup checks row existence, not body, so it works as before.

Fix

Read the html part instead of the body container:

body: mail.html_part ? mail.html_part.body.to_s : mail.body.to_s,

Pure plain-text mailers (no html part) fall back to mail.body as before.

Testing

Extended the MemberMailer#chaser logging spec to assert the persisted row has a body containing the template copy. Confirmed red→green: the assertion fails with "" on master and passes with the fix. Full mailer specs and the three-month chaser service spec pass (85 examples), RuboCop clean.

Context

Found while diagnosing chaser reliability for #2384 (chaser introduced in #2449 for #2383).