Determine if Aliases are required in the spec

As a working group we've discussed the potential need for having aliases to facilitate codegen use-cases.

Currently, when referencing an operationId within a source specification document, you MUST prefix it with the source name if more than one source exists to avoid collisions. This is stated as follows in the spec:

If more than one source document is defined within a Workflows document, then the operationId specified MUST be prefixed with the source name to avoid ambiguity or potential clashes.

While the above approach ensures clarity within the Workflows Specification, it does not necessarily help codegen tools form figuring out how to name source1.opName and source2.opName to two different meaningful class or function names.

Should we add the ability to support aliases within the core spec, or perhaps we should auto an official codegen extension for the specification.