Currently NostrDB does not seem to handle encryption/decryption of DMs.
Since NostrDB now controls the block parsing process and fetches note
contents directly from the database, we have to add a specific condition
that injects decrypted content directly to the ndb content parser.
This is done in conjunction with some minor refactoring to `NdbBlocks`
and associated structs, as in C those are separated between the content
string and the offsets for each block, but in Swift this is more
ergonomically represented as a standalone/self-containing object.
No changelog entry is added because the previously broken version was
never released to the public, and therefore this fix produces no
user-facing changes compared to the last released version.
Changelog-None
Closes: https://github.com/damus-io/damus/issues/3106
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
