Previously it was required that a directory path is provided to the import API.
Now it is possible to point directly to the .asc file containing a secret key.
This allows UI to present a file selection dialog to the user
and let select the file directly.
Selecting a directory is still supported for backwards compatibility.
It can be used e.g. as a default in the file saving dialog. Also display the original filename in
the message info. For these purposes add Param::Filename in addition to Param::File and use it as an
attachment filename in sent emails.
Opening the same account (context) from multiple processes is dangerous, can result in duplicate
downloads of the same message etc. Same for account manager, attempts to modify the same
accounts.toml even if done atomically with may result in corrupted files as atomic replacement
procedure does not expect that multiple processes may write to the same temporary file.
accounts.toml cannot be used as a lockfile because it is replaced during atomic update. Therefore, a
new file next to accounts.toml is needed to prevent starting second account manager in the same
directory.
But iOS needs to be able to open accounts from multiple processes at the same time. This is required
as the "share-to-DC extension" is a separate process by iOS design -- this process may or may not be
started while the main app is running. Accounts are not altered however by this extension, so let's
add to the `Accounts::new()` constructor an `rdwr` parameter which allows to read the accounts
config w/o locking the lockfile.
Message.set_text() and Message.get_text() are modified accordingly
to accept String and return String.
Messages which previously contained None text
are now represented as messages with empty text.
Use Message.set_text("".to_string())
instead of Message.set_text(None).
When running `cargo test` in the deltachat-jsonrpc folder,
a new file `openrpc/openrpc.json` will be created with an
[OpenRPC](https://spec.open-rpc.org/) definition.
It can be copy-pasted into the
[OpenRPC playground](https://playground.open-rpc.org/)
and used to generate clients in other languages.
This way is more compatible to JSON-RPC libraries
that do not support receiving notifications from the server
and allows describing event types in the OpenRPC specification.
Event thread converting events to notifications in the FFI
is removed, so it is now possible to construct a dc_jsonrpc_instance_t
while still retrieving events via dc_event_emitter_t.
