MTLS support for the Python client

[ZPascal]

Proposal:
We should also support mutual TLS for the InfluxDB client. The implementation could be handled as a quick win and I can prepare the corresponding functionality inside a PR. The client uses urllib3 as a library to establish a connection to the InfluxDB and the MTLS support is already implemented inside it. Currently, there are two possible ways to implement the MTLS support inside the client:

1. Forward the custom Python SSL context to the urllib3 via the **kwags functionality (Personal favorited implementation, more adaptable)
2. Use the same functionality as the normal TLS implementation and forward the certificates to the urllib3

Current behavior:
Currently, it's possible to define e.g. a Python SSL context as **kwags but this context is not forwarded to all calls at the end.

Desired behavior:
I would expect that MTLS is also supported by the library.

Use case:
The use case is the possibility to establish an MTLS connection to the InfluxDB.

[bednar]

Hi @ZPascal,

thanks for using our client and your proposal.

The implementation could be handled as a quick win and I can prepare the corresponding functionality inside a PR.

I will be happy to review your PR... btw every PR is welcome.

1. Forward the custom Python SSL context to the urllib3 via the **kwags functionality (Personal favorited implementation, more adaptable)

How will it works together with ssl_ca_cert option?

Regards

[ZPascal]

Hi @bednar, I would expect that the variable is None (if you did not specify a certificate) and at the end not really used inside the connection pool manager.

I can also maybe implement inside the PR the full MTLS support delivered by classical shipped certs via the configuration. The framework is already there and used but not mapped to the configuration option/ initialization. :)

So in the end, the user got the option to use one of both possibilities.

[bednar]

@ZPascal it sounds good 👍

I will be happy to review and merge your PR ;)

[ZPascal]

Hi @bednar, thank you for merging the PR. Could you please share with me the timeline to publish the new release version?

[bednar]

@ZPascal you can use current dev version by: pip install git+https://github.com/influxdata/influxdb-client-python.git@master. The production version will be released at the end of the month.

[ZPascal]

@bednar Thank you for the info. I've got already a wheel file on my side to consume the change. I just wanted to know when I can replace it :)