A caller passing basePath '/' produced //api/email/..., which a browser reads as a protocol-relative URL rather than a path. Strip the slashes first and only add a prefix when something is left.
replaceCidReferences rewrote cid: references to /email/:id/attachment/:file,
which matches no route: attachments are served from the API server, mounted
at ${basePath}/api. When MailDev sits under a subpath the prefix was missing
as well, which is the setup described in #439.
Emit ${basePath}/api/email/:id/attachment/:file, root-relative by default, and
thread the API server's basePath through getEmailHtml. baseUrl still prefixes
//host for a caller that passes it.
On the current code this does not change what the web UI shows for a typical
message: mailparser already inlines related parts as data: URIs, and a cid:
that survives parsing is one that matches no attachment. replaceCidReferences
is exported from @maildev/smtp, though, so the URL it builds should resolve.
Refs #439
dualfroz