Makes upload_file cleaner (context manager instead of try-finally)
and helps keep the logic "we may own this stream and need to close
it or not" separated.
It can be overengineered to allow nesting the same instance in
context managers and also provide implementations for synchronous
context managers but it adds quite a bit of unnecessary complexity
for the time being. YAGNI.
Only the uses of `isinstance` against `InputPeer*` types were
reviewed. Notably, `utils` is exempt on this because it needs
to deal with everything on a case-by-case basis.
Since the addition of `*FromMessage` peers, any manual `isinstance`
checks to determine the type were prone to breaking or being
forgotten to be updated, so a common `helpers._entity_type()`
method was made to share this logic.
Since the conversion to `Peer` would be too expensive, a simpler
check against the name is made, which should be fast and cheap.
It's the only way to properly clean all background tasks,
which the library makes heavy use for in MTProto/Connection
send and receive loops.
Some parts of the code even relied on the fact that it was
asynchronous (it used to return a future so you could await
it and not be breaking).
It's automatically syncified to reduce the damage of being
a breaking change.
* Create `_NOT_A_REQUEST` when needed. Currently, modifications
in the raised exception would be "global".
* `retries` parameters were actually attempts. This has been fixed
to actually be the amount of retries, so 0 now means don't retry.
* Helper function to deal with retries instead of using a range with
different styles every time.
This means that the TcpClient and the Connection (currently only
ConnectionTcpFull) will no longer be concerned about handling
errors, but the MTProtoSender will.
The foundation of the library will now be based on asyncio.
