Access to InfluxDB Cloud instance via custom URL and certificate

__Proposal:__
Allow access to our InfluxDB Cloud instance via CNAME and ability to upload Server Certificate.

__Current behavior:__
Only access is via AWS EC2 instance URL (somewhat cryptic).

__Desired behavior:__
Use a URL like https://influxdb.groov.com (CNAME in place now) to access my InfluxDB Cloud instance. Also, would like to upload our wildcard server certificate to ensure encrypted connection.

__Alternatives considered:__
None at this time.

__Use case:__
We are manufacturer and developer of industrial automation and IIoT products for manufacturing, OEM machine builders, building management, and SCADA applications (www.opto22.com). We'd like to demonstrate the capabilities of InfluxDB Cloud to our customers, so they can begin leveraging the power of your solution. There is significant demand for this solution, particularly for IIoT and digital transformation projects.

The issue names no repository files, tests, or entry points. First determine whether custom URLs and certificate uploads are implemented in this repository or managed in InfluxDB Cloud infrastructure. Done means a Cloud instance can use the requested CNAME and uploaded wildcard certificate for an encrypted connection.

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