Add extra environment variables for SSL encryption to the database

[crimmy68]

Related Issue: #1105

New Behavior

As suggested by someone else in #1105 , I added extra environment variables for the docker image:

• DB_CLIENT_SSL_CERT
• DB_CLIENT_SSL_KEY
• DB_CLIENT_SSL_CA

Contrast to Current Behavior

Unable to provide parameters to use SSL encryption to external Postgresql database.

Discussion: Benefits and Drawbacks

Providing these extra environment variables is completely optional so there is no drawback.
However it provides the benefit of providing the option when filling in the extra.py is not an option.
( I don't want to edit code for Kubernetes deployments f.e. )

Changes to the Wiki

N/A

Proposed Release Note Entry

Simply mention the extra options.
potentially a reference to: https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-PARAMKEYWORDS

Double Check

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• I have explained my PR according to the information in the comments.
• My PR targets the develop branch.