Tomodachi

- Added an additional way of gracefully triggering shutdown of a running service, by using the new `tomodachi.exit()` function, which will initiate the termination processing flow in the same way as signaling `SIGINT` or `SIGTERM`. The `tomodachi.exit()` call can additionally take an optional exit code as an argument to support new ways of catching service operation.
- The process' exit code can also be altered by changing the value of `tomodachi.SERVICE_EXIT_CODE`, however using the new `tomodachi.exit` call with an integer argument will override any previous value set to `tomodachi.SERVICE_EXIT_CODE`. The default value is set to `0`.

- Handle exceptions lower in the stack for messaging services (AMQP and AWS SNS+SQS handlers), which now allows catching exceptions in middlewares, which was previously not possible. (github: **justcallmelarry**)
- Improved documentation for uses of `tomodachi.get_service` (github: **jmfederico**)
- Type hint annotation improvements.

- Adds the possibility to add a function called `_stopping_service` to the `tomodachi` Service class, which is run as soon as a termination signal is received by the service. (github: **justcallmelarry**)
- Fix for potential exceptions on botocore session client raising a `RuntimeError`, resulting in a tomodachi "Client has never been created in the first place" exception on reconnection to AWS APIs.
- Added Python 3.10 to the CI test matrix run via GitHub Actions.
- Additional updates for compatibility with typing libraries to improve support for installations on Python 3.10.
- Supports `aiohttp` 3.8.x versions.
- Supports `tzlocal` 3.x and 4.x releases.

- Pins `aiobotocore` to use up to 1.3.x releases, since the 1.4.x versions session handling currently causes issues when used.

- Now pins the `tzlocal` version to not use the 3.x releases as it would currently break services using scheduled functions (the `schedule` decorator, et al) if `tzlocal` 3.0 is installed.
- Updated classifiers to identify that the library works on Python 3.10.
- Added the new `Framework :: aiohttp` classifier.

- If a `PYTHONPATH` environment value is set and a service is started without the `--production` flag, the paths specified in `PYTHONPATH` will be added to the list of directories to watch for code changes and in the event of any changes done to files on those directories, the service will restart. Previously only code changes in the directory or sub directory of the current working directory + the directory of the started service (or services) were monitored.
- The `topic` argument to the `tomodachi.aws_sns_sqs` decorator is now optional, which is useful if subscribing to a SQS queue where the SNS topic or the topic subscriptions are set up apart from the service code, for example during deployment or as infra.