Previous behaviour: connection with IDLE was stopped every 5 minutes to
poll the other threads. As a result messages received within that time
window when there was no IDLING were never received.
Current behaviour: polling is done in the main connection.
The operation() method on the MailBackend trait returns a trait object
that can read or modify an Envelope directly from the backend. This is
used to get eg the envelope's text, or set flags. It has two arguments,
envelope hash and folder hash.
Only the Maildir backend needed the latter argument, and it can be replaced with a dictionary to match envelope hashes to folder hashes within the Maildir backend.
Envelope can now only be accessed from within a RwLock. Two new structs
are introduced: EnvelopeRef and EnvelopeRefMut. These hold a reference
to an Envelope and the mutex guard that keeps them alive.
This change allows sharing of the envelopes hash map amongst threads.
Add a boolean field to accounts that states if the account can be
accessed. Local backends (Maildir/mbox) return true every time, but
remote backends (IMAP) may not. Accounts start as offline and then get
initialised when their status goes to online. Right now if an IMAP
account startup but later get offline, there are crashes. With this
change the account can be switched back to offline when that happens.
Adds support for contacts (Cards) marked as `external_resource` which
prevents modifications from happening. No way to import external
contacts is added yet.
CardId is the "Primary Key" of the contact type, Card. Meli-created
contacts had UUIDs for their CardId. In order to import external
contacts and ensure their primary key is the same each time, CardId is
made into an enum to add hashing as a choice.
At a certain point when expecting a line terminator parts() checks for
'\n' but not '\r\n'. This resulted in all multipart attachments coming
from b"\r\n" sources like IMAP having only one part when parsed.
Attachment needs to know the range of bytes where the body part of the
attachment is located. The Attachment.raw field contains the entire
attachment, headers and body. The new Attachment.body fields contains a
`StrBuilder` which contains the offset and length of the body part inside
`raw`.
