Add ability to disable mTLS

[klurpicolo]

Description

Add option to disable mTLS

Fixes (issue)

Type of change

Please select all options that apply to this change:

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Bug fix (non-breaking change which fixes an issue)
• Documentation update

Checklist:

Confirm you have completed the following steps:

• My code follows the style of this project.
• I have performed a self-review of my code.
• I have made corresponding updates to the documentation.
• I have added/updated unit tests to cover my changes.
• I have added/updated integration tests to cover my changes.

[patrickdemers6]

fleet-telemetry relies upon the device's certificate for its identify. With this implementation, won't extractCertFromHeaders panic since r.TLS would be nil?

fleet-telemetry/server/streaming/server.go

Lines 237 to 244 in c6050ed

	func extractCertFromHeaders(r *http.Request) (*x509.Certificate, error) {
	nbCerts := len(r.TLS.PeerCertificates)
	if nbCerts == 0 {
	return nil, fmt.Errorf("missing_certificate_error")
	}
	return r.TLS.PeerCertificates[nbCerts-1], nil
	}