Add support for offline Entity create and update

[lognaturel]

Spec discussion at https://forum.getodk.org/t/form-spec-proposal-support-entity-updates-from-multiple-offline-clients/47890

We are going to stage this. In the next version of pyxform, users will need to explicitly opt in to produce forms that use the v2024.1.0 spec to use offline Entities to allow for some piloting of the functionality across all components. The opt-in flag will be removed in the following version and all Entity-related forms will be produced following the v2024.1.0 spec.

Entity-related forms can create or update Entities or do both. There is existing logic in pyxform to determine which of these a form definition specifies.

Forms that can create Entities

For forms that can create Entities, the only change needed in pyxform is to set the entities-version attribute on the model node to 2024.1.0.

Forms that can update Entities

For forms that can update Entities, the entities-version attribute on the model node will need to be set to 2024.1.0.

Additionally:

• Add trunkVersion and branchId attributes to the entity element
• Add the following binds:

<bind nodeset="/data/meta/entity/@trunkVersion" type="string" calculate="instance('trees')/root/item[name=/data/tree]/__trunkVersion" />
<bind nodeset="/data/meta/entity/@branchId" type="string" calculate="instance('trees')/root/item[name=/data/tree]/__branchId" />

Opt in

Initially, the changes described above should be opt-in so we also need to introduce a setting column named offline on the entities sheet. It should be optional and its default value should be no/false. If its value is set to yes, the changes above should be applied. Otherwise, Entity forms should be generated as they are today.

[tiritea]

Will be interested to follow spec evolution