feat: Support for `ibis.dtype("geospatial:geometry")`

Is your feature request related to a problem?

I wanted to store the schema of a table in a json file so that I can easily compare/convert new data extractions to the existing schema. If I try to convert the schema to a regular dictionary and back I get an error:

pairs = {n: str(t) for n, t in table.schema().fields.items()}
ibis.schema(pairs)

Output:

SignatureValidationError: Schema({'id': 'String', 'created_at': 'String', 'updated_at': 'String', 'removed': 'Boolean', 'description': 'Null', 'location': 'GeoSpatial', 'user_by_created_by': 'Struct', 'campaign': 'Struct', 'postertype': 'Null'}) has failed due to the following errors:
  `fields`: {'id': 'String', 'created_at': 'String', 'updated_at': 'String', 'removed': 'Boolean', 'description': 'Null', 'location': 'GeoSpatial', 'user_by_created_by': 'Struct', 'campaign': 'Struct', 'postertype': 'Null'} is not matching GenericMappingOf(key=InstanceOf(type=<class 'str'>), value=CoercedTo(type=<class 'ibis.expr.datatypes.core.DataType'>, func=<bound method DataType.__coerce__ of <class 'ibis.expr.datatypes.core.DataType'>>), type=CoercedTo(type=<class 'ibis.common.collections.FrozenOrderedDict'>, func=<class 'ibis.common.collections.FrozenOrderedDict'>))

Expected signature: Schema(fields: FrozenOrderedDict[str, DataType])

If I remove geospatial: from the type, it works:

pairs = {n: str(t).replace("geospatial:", "") for n, t in table.schema().fields.items()}
ibis.schema(pairs=pairs)

Output:

ibis.Schema {
  id                  string
  created_at          string
  updated_at          string
  removed             boolean
  description         null
  location            geospatial:geometry
  user_by_created_by  struct<email: string, id: string, name: string>
  campaign            struct<country: string, election: struct<electionDay: string, id: string, name: string>, id: string, name: string, region: string>
  postertype          null
}

What is the motivation behind your request?

No response

Describe the solution you'd like

I'd like all string conversions of datatypes to convert back to the original type when used in ibis.dtype()

What version of ibis are you running?

9.5.0

What backend(s) are you using, if any?

DuckDB with spatial extension

Code of Conduct

[X] I agree to follow this project's Code of Conduct

ibis-project / ibis

feat: Support for `ibis.dtype("geospatial:geometry")` #10170