Improve validation messages for values that are templated.

[benbz]

If we have values that are passed to tpl but are absent we get appalling errors, even if other templates require them. Add a blank template that is evaluated first that collects basic validation errors and if any are present fails prior to tpl being called.

Before:

$ helm template ess charts/matrix-stack

Error: template: matrix-stack/templates/well-known/ingress.yaml:18:4: executing "matrix-stack/templates/well-known/ingress.yaml" at <include "element-io.ess-library.ingress.tls" (dict "root" $ "context" (dict "host" $.Values.serverName "ingress" .ingress "ingressName" "well-known"))>: error calling include: template: matrix-stack/templates/ess-library/_ingress.tpl:42:10: executing "element-io.ess-library.ingress.tls" at <include "element-io.ess-library.ingress.tlsHostsSecret" (dict "root" $root "context" (dict "hosts" (list $host) "tlsSecret" $ingress.tlsSecret "ingressName" $ingressName))>: error calling include: template: matrix-stack/templates/ess-library/_ingress.tpl:57:12: executing "element-io.ess-library.ingress.tlsHostsSecret" at <$host>: wrong type for value; expected string; got interface {}

Use --debug flag to render out invalid YAML

After:
$ helm template ess charts/matrix-stack

Error: execution error at (matrix-stack/templates/z_validation/validation.txt:40:3):

• elementWeb.ingress.host is required when elementWeb.enabled=true
• matrixAuthenticationService.ingress.host is required when matrixAuthenticationService.enabled=true
• matrixRTC.ingress.host is required when matrixRTC.enabled=true
• synapse.ingress.host is required when synapse.enabled=true
• serverName is required when synapse.enabled=true
• serverName is required when wellKnownDelegation.enabled=true

Use --debug flag to render out invalid YAML

[github-actions]

dyff of changes in rendered templates of CI manifests

No changes in rendered templates