Add Helm template validation for mutually exclusive namespace flags (#65)

* Initial plan

* Add template-time validation for mutually exclusive namespace flags

Co-authored-by: bdehamer <398027+bdehamer@users.noreply.github.com>
Agent-Logs-Url: https://github.com/github/deployment-tracker/sessions/ab6214f1-4681-454f-b5de-7d0caa1a9cc9

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: bdehamer <398027+bdehamer@users.noreply.github.com>

Author: Copilot

deploy/charts/deployment-tracker/templates/deployment.yaml

@@ -1,3 +1,6 @@
+{{- if and .Values.config.namespace .Values.config.excludeNamespaces }}
+{{- fail "config.namespace and config.excludeNamespaces are mutually exclusive and cannot both be set" }}
+{{- end }}
 apiVersion: apps/v1
 kind: Deployment
 metadata: