projjson pydantic model

[d-v-b]

adds a pydantic model for projjson

[d-v-b]

@emmanuelmathot some comments on the geo proj spec based on the work here:

• the spec states that the "version" key is required, but several JSON examples in the spec don't have it, e.g. https://github.com/EOPF-Explorer/data-model/blob/main/attributes/geo/proj/README.md#explicit-declaration, https://github.com/EOPF-Explorer/data-model/blob/main/attributes/geo/proj/README.md#example-1-simple-web-mercator-raster-group-level
• There is ambiguity between fields that can be null OR unset (like "code", "wkt2", "projjson") vs fields that cannot be null and can only be unset ("bbox", "transform", "spatial_dimensions"). Is the intention to treat {"field": null} as equivalent to {}? If so, this should be stated early in the spec, and every optional field should take null as a valid value.
• PROJJSON has a json schema that we can refer to, so we don't need to say that the type of the "projjson" field is any.

[d-v-b]

also:

• "bbox" is defined relative to the CRS defined by the "code", "projjson", or "proj.wkt2" fields. But all of those fields are optional. If none of those fields are set, how should the "bbox" field be interpreted? Should it be ignored, or is it it an error for "bbox" to be set when a CRS was not declared?

[emmanuelmathot]

• we can update the examples
• To me when not specified, null, empty or {} are the same.
• projjson can be updated to projjson object.
• At least one of the fields MUST be specified, but it is RECOMMENDED to provide more information so that, for example, GDAL can read your data without issues.

[d-v-b]

• At least one of the fields MUST be specified, but it is RECOMMENDED to provide more information so that, for example, GDAL can read your data without issues.

I don't think this language is in the spec right now. For each of the 3 CRS fields, it says:

This field SHOULD be set to null in the following cases:

    The asset data does not have a CRS, such as in the case of non-rectified imagery with Ground Control Points.

[d-v-b]

should I open a PR to add the requirement that at least one of the 3 fields is set?

[emmanuelmathot]

yes please

[emmanuelmathot]

#44