Add --with-proxysql flag to single sandbox deployment

[renecannao]

Summary

• Adds --with-proxysql flag to dbdeployer deploy single command
• When set, deploys a ProxySQL instance alongside the single MySQL sandbox with one backend in hostgroup 0 (no readers)
• Follows the same pattern used in cmd/replication.go, calling sandbox.DeployProxySQLForTopology with nil for slavePorts

Test plan

• dbdeployer deploy single --help shows --with-proxysql flag
• dbdeployer deploy single <version> --with-proxysql deploys ProxySQL in proxysql/ subdirectory
• ProxySQL is configured with single backend on hostgroup 0
• Regular dbdeployer deploy single <version> (without flag) still works as before

Closes #41

[gemini-code-assist]

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Configuration used: Organization UI

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Run ID: 4e6233a6-70e8-4b5c-8eca-dc9793cdf0a3

📥 Commits

Reviewing files that changed from the base of the PR and between 5402472 and 2d2a495.

📒 Files selected for processing (1)

• cmd/single.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch phase2b/task6-single-with-proxysql

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[Copilot]

Pull request overview

Adds an opt-in --with-proxysql flag to the dbdeployer deploy single command so that a ProxySQL instance is deployed alongside a newly created single sandbox, using the existing sandbox.DeployProxySQLForTopology helper (single backend in hostgroup 0).

Changes:

• Add --with-proxysql persistent flag to deploy single.
• After creating the standalone sandbox, optionally deploy ProxySQL into a proxysql/ subdirectory using the single sandbox’s port from its sandbox description.

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[Copilot]

The sandbox directory calculation doesn’t match the logic used in sandbox.createSingleSandbox when sd.DirName is empty. In particular, if the user supplies --binary-version and the basedir directory name differs from sd.Version (e.g. basedir name contains dots or other characters), createSingleSandbox uses defaults.Defaults().SandboxPrefix + sd.BasedirName (no VersionToName conversion), but this code applies common.VersionToName(origin) and can point to a non-existent directory. Consider mirroring the exact directory naming logic from createSingleSandbox: if sd.DirName is empty, build the dir name based on whether sd.Version != sd.BasedirName and only apply VersionToName to sd.Version in the sd.Version == sd.BasedirName case.

Suggested change

	origin := args[0]
	if args[0] != sd.BasedirName {
	origin = sd.BasedirName
	}
	sandboxDir := path.Join(sd.SandboxDir, defaults.Defaults().SandboxPrefix+common.VersionToName(origin))
	if sd.DirName != "" {
	sandboxDir = path.Join(sd.SandboxDir, sd.DirName)
	var sandboxDir string
	if sd.DirName != "" {
	// If a custom directory name was specified, use it directly.
	sandboxDir = path.Join(sd.SandboxDir, sd.DirName)
	} else {
	// Mirror the naming logic from createSingleSandbox when DirName is empty.
	prefix := defaults.Defaults().SandboxPrefix
	if sd.BasedirName != "" && sd.Version != sd.BasedirName {
	// When the basedir name differs from the version (e.g. provided via --binary-version),
	// use the basedir name as-is without applying VersionToName.
	sandboxDir = path.Join(sd.SandboxDir, prefix+sd.BasedirName)
	} else {
	// When the basedir name matches the version (or is empty), apply VersionToName to the version.
	sandboxDir = path.Join(sd.SandboxDir, prefix+common.VersionToName(sd.Version))
	}