Add support for Trigger Authentication for InfluxDB

[acobaugh]

This allows authToken, serverURL, and organizationName to be sourced from TriggerAuthentication and ClusterTriggerAuthentication by the influxdb scaler.

Relates to #1905
Relates to #1892

Checklist

• Commits are signed with Developer Certificate of Origin (DCO - learn more)
• Tests have been added
• [n/a] A PR is opened to update our Helm chart (repo) (if applicable, ie. when deployment manifests are modified)
• A PR is opened to update the documentation on (repo) (if applicable)
• Changelog has been updated

[acobaugh]

I believe the docs can be left as-is since I think this PR just brings the code in line with the documented behavior. Otherwise I can go ahead and get a PR worked up for that as well.

[tomkerkhove]

This allows authToken, serverURL, and organizationName to be sourced from TriggerAuthentication and ClusterTriggerAuthentication by the influxdb scaler.

I don't want to be a pain, but it should only be used for authentication information, unless the auth token is specific to the server URL + org combination of course. WDYT @zroubalik ?

Based on the outcome here, we'd need a PR on our docs as well

[zroubalik]

This allows authToken, serverURL, and organizationName to be sourced from TriggerAuthentication and ClusterTriggerAuthentication by the influxdb scaler.

I don't want to be a pain, but it should only be used for authentication information, unless the auth token is specific to the server URL + org combination of course. WDYT @zroubalik ?

Based on the outcome here, we'd need a PR on our docs as well

I am fine with including url and organization name, but it's up to you @tomkerkhove
If we add these the docs will be need an update

[tomkerkhove]

LGTM, but we'll need a PR on https://github.com/kedacore/keda-docs.

Would be nice if you could fix the docs in previous versions to remove TA support since it's not the case