Override configuration (fixed, but without docs)

Hi,
i have an ssl error which i can solve by insert my own certificate to your API client,
but i don't find a way to override your configuration file.
[Conf file](https://github.com/devopshq/teamcity/blob/develop/dohq_teamcity/configuration.py)
field name = **self.ssl_ca_cert = None**
thanks,
Bar Aluf

Read dohq_teamcity/configuration.py and inspect the self.ssl_ca_cert = None entry to understand the existing configuration override behavior. Document how a caller supplies a custom certificate, and verify that the documentation clearly covers the SSL error workaround and the configuration field.

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