@Header("'foo.bar'") looks for a header ''foo' with property bar'

[garyrussell]

See https://stackoverflow.com/questions/58403246/header-annotation-with-in-header-name-such-as-headerfoo-bar-doesnt-m/58414528#58414528

When @Header("'foo.bar'") is used, we end up with:

#target.handleMessage(payload, #requiredHeader(headers, ''foo').bar')