Enable migrations from older database schemas.

[evetion]

Fixes Deltares/Ribasim-NL#138

This has no schema version (stored in the geopackage) yet, but this is something we could implement in the future.

[deltamarnix]

I would like to opt to add a geopackage version in this PR and let's call everything that doesn't have it version 0, and from now on we will write a modelversion: 1. Otherwise we might get conflicts when we figure out that more backwards compatibility is required in the coming months. Then while writing migration, first check if the version is correct.

• change QGIS writing
• change Ribasim python writing
• Write the geopackage version during migration if it was successful? (Maybe not, since it's only in memory migration)
• Check in your migration code what the version is to migrate

For now, let's keep it as simple as you have it, although I would rather see a pipeline that migrates step by step. But that's for another moment in time.

[visr]

This doesn't yet include removing listen_node_type columns:

ValidationError: 1 validation error for TableModel[DiscreteControlVariableSchema]
df
  Value error, Unrecognized column 'listen_node_type'.

[evetion]

@deltamarnix This now writes the schema version to the geopackage (also from QGIS), which is used to check whether to migrate or not. @visr This now also migrates the other tables with listen_node_type.

[deltamarnix]

I want to see tests for the migration and the writing of the version files (both qgis and ribasim python)

[deltamarnix]

If @SnippenE agrees that loading an old model in QGIS does not do the migration, but crashes instead, I am okay with the changes so far.