charts/gateway several updates

[gvermeulen7205]

Description of the change

• Updated MySQL SubChart, existing MySQL Chart is deprecated
• Added External Secret Management for Gateway Configuration, DefaultSSLKey, license and bundles
• Added bundle references to existing Kubernetes ConfigMaps/Secrets allowing more separation of concern between deployment and configuration
• Added a mount for system.properties
• Updated TLS configuration
• Updated Ingress Configuration (Structure + API Version support)
• Added NodeSelector and Affinity Configuration
• Added HostAliases for overriding /etc/hosts
• Updated Documentation

Benefits

• External secret management (alternative is writing everything in values.yaml..)
• Additional configuration options

Drawbacks

• If upgrading from a previous version of this Chart and you are using the built-in mysql subChart - you will lose that database. A backup recommendation has been added to the readme.

The following may also affect existing installations, the recommended approach added to the readme is to inspect the latest values.yaml and apply the relevant updates prior to performing an upgrade.

• tls section has changed
• ingress object has changed

Checklist

• [x] Chart version bumped in Chart.yaml according to semver.
• [x] Variables are documented in the README.md
• [x] Title of the PR starts with chart name (e.g. [charts/gateway])
• [x] If the chart contains a values-production.yaml apart from values.yaml, ensure that you implement the changes in both files

[gvermeulen7205]

looks good.

may want to bump the version to 2.1.0. it is quite big difference compare to previous version

Thanks @alisterz - I've got version changes planned for the next iteration which will include more detailed documentation references in the Wiki (when created).