Allow Helm templating for proxyPass value

[leninmehedy]

Problem

Recently added proxyPass variable does not support templating, which requires hardcoding the value in the values.yaml file or use --set command to set it explicitly as http://<RELEASE_NAME>-rest.

However, it would have been better if the value could be set as template, e.g. http://{{ .Release.Name }}-fst.

Relevant issue: hashgraph/full-stack-testing#410

Solution

• Allow proxyPass value to be a template e.g. http://{{ .Release.Name }}-fst.
• Use tpl function to render the template while creating the configmap here

Alternatives

Without supporting the templating, end-user always needs to update the values.yaml file or use --set hedera-explorer:.proxyPass=<NEW VALUE> during deployment of their chart with a new release name.

Blocks

• fix: avoid hardcoding mirror-node-explorer rest API in values.yaml full-stack-testing#413