Modify the Ewoks schema specification

When changing the Ewoks schema specification, a new schema version needs to be added to the dictionary returned by get_versions in src/ewokscore/graph/schema/__init__.py.

The dictionary contains the schema version metadata (more on this below) indexed by versions in increasing order.

def get_versions() -> Dict[Version, SchemaMetadata]:
    [...]

    return {
        parse_version("0.0"): SchemaMetadata(("0.0", "0.0.1"), v0_update),
        parse_version("1.0"): SchemaMetadata(("0.1.0-rc", None), from_v1_0_to_v1_1),
        parse_version("1.1"): SchemaMetadata(("0.1.0-rc", None), None),
    }

The latest version is defined by the last entry in the dictionary

Define the new version number

When adding a new schema version, the schema version must be incremented with respect to the last get_versions entry depending on the change:

• When adding a backward-compatible change (e.g. a new optional field), the minor part of the version should be incremented (e.g. go from 1.0 to 1.1)

• When adding a breaking change (e.g. a new required field or a change in structure), the major part of the version should be incremented (e.g. go from 1.1 to 2.0).

Add the new version number

To add a new version, add an entry in the dictionary returned by get_versions with:

• the version number as the key (stored as Version)

• an instance of SchemaMetadata as value.

The SchemaMetadata creation needs two arguments:

• ewokscore version bounds (stored as a 2-tuple of Version): the first tuple value is the lowest ewokscore version that supports this schema, the second is the highest version that supports this schema (put None if there is no upper bound).

• a function that converts this schema version to the next version. The function can be defined in the update submodule. If the version is the latest one, put None since there is no next version.