Add version property to M3 Metamodel

[enikao]

Based on discussion on 2023-03-03 and #7, we add the property version: integer to Metamodel.

[ftomassetti]

Are there constraints on this value? Should it be >= 1?

[enikao]

I'd say so --> Will update docs

[enikao]

Is version an integer or string?

See also LionWeb-io/lionweb-java#46 (comment)

From #99 (comment):

I think for M3 it makes sense to define version as integer, so we can apply language migrations in a well-defined way. If we made it a string and encounter versions 1-trial and 1-beta, we cannot establish a clear migration path.

Regarding serialization:

Because we use JSON string type everywhere (and never JSON number type). Maybe someone wants to have a version with more than 53 digits? (-;

[ftomassetti]

I think we need a decision about integer vs string

[enikao]

Do we want to discuss this in the meeting or just here?

[ftomassetti]

I would say that a poll would be enough

[enikao]

I think we first need to decide on #130 before we can decide this.

[enikao]

Decision: version is a string
See #130 for details.