Symphony-bdk-python

**Features**
251 268 Extensibility mechanism and Groups API extension
270 Enabled DFv2 by default, logged a deprecation notice when DFv1 used

**Dependency upgrades**
264 265 Upgraded openapi generator and re-generated api and models classes from swagger specs
272 Upgraded urllib3, pyyaml

**Documentation**
267 Provided example to import message with attachment
269 Updated PyPI package name in the getting started guide

Fixes:
256 BDK not retrying on timeout errors

**Features**
249: Improve suspend user API

**Dependency upgrades**
246: aiohttp, tenacity
257: cryptography and other minor upgrades

**Documentation**
250: Update documentation regarding certificate formats for cert authentication
252: Clarified in the docs listeners must be async
253: Documented how to achieve full concurrency across several DF events
254: Added proxy configuration example

**Features**
239: Added support for updateIM and getIMInfo endpoint
241: Support of message update endpoint

**Documentation**
240: BDK to SDK renaming when referring to legacy SDK

**Features**
234: Update Room V3 API to Pin/Unpin a message

**Bug fixes**
235: When getting text content, we now extract the escaped content and then unescape characters

**Documentation**
232: Wrote migration guide from BDK 1.x to BDK 2.0
229: Cleaned up readme file and documentation after 2.0.0 release