Add support for services

[stevespringett]

see the docs: https://cyclonedx.org/use-cases/#service-definition

[jkowalleck]

implementation detail:

• services have support for bom-ref and bom. Therefore the bom properties need to be discriminated. see

  cyclonedx-javascript-library/src/serialize/baseSerializer.ts

  Lines 25 to 41 in b2abc1b

  	#getAllBomRefs (bom: Bom): Iterable<BomRef> {
  	const bomRefs = new Set<BomRef>()
  	function iterComponents (cs: Iterable<Component>): void {
  	for (const { bomRef, components } of cs) {
  	bomRefs.add(bomRef)
  	iterComponents(components)
  	}
  	}
  	if (bom.metadata.component !== undefined) {
  	bomRefs.add(bom.metadata.component.bomRef)
  	iterComponents(bom.metadata.component.components)
  	}
  	iterComponents(bom.components)
  	return bomRefs.values()
  	}