Add support for GeoInterface CRS metadata

[eliascarv]

Waiting for JuliaGeo/GeoInterface.jl#161
Closes #24

Test code:

julia> using GeoParquet, DataFrames

julia> df = GeoParquet.read("example.parquet")
5×6 DataFrame
 Row │ pop_est         continent      name                      iso_a3   gdp_md_est  geometry                          
     │ Float64?        String?        String?                   String?  Int64?      WellKnow…                         
─────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────
   1 │ 889953.0        Oceania        Fiji                      FJI            5496  WellKnownBinary{Geom, Vector{UIn…
  ⋮  │       ⋮               ⋮                   ⋮                 ⋮         ⋮                       ⋮
                                                                                                         4 rows omitted

julia> metadata(df, "GEOINTERFACE:geometrycolumns")
(:geometry,)

julia> metadata(df, "GEOINTERFACE:crs")
GeoFormatTypes.ProjJSON(...)

[asinghvi17]

Does the ProjJSON type work with a Dict? I'm pretty sure it would have to be a String...at least to be passed to GDAL.

[eliascarv]

Yes, ProjJSON type supports Dicts and Strings:
https://github.com/JuliaGeo/GeoFormatTypes.jl/blob/master/src/GeoFormatTypes.jl#L193-L213

[eliascarv]

And GeoParquet.write does not works very well when ProjJSON is passed as String:

julia> using GeoParquet, Parquet2, DataFrames, JSON3, GeoFormatTypes

julia> df = GeoParquet.read("example.parquet")
5×6 DataFrame
 Row │ pop_est         continent      name                      iso_a3   gdp_md_est  geometry                          
     │ Float64?        String?        String?                   String?  Int64?      WellKnow…                         
─────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────
   1 │ 889953.0        Oceania        Fiji                      FJI            5496  WellKnownBinary{Geom, Vector{UIn…
  ⋮  │       ⋮               ⋮                   ⋮                 ⋮         ⋮                       ⋮
                                                                                                         4 rows omitted

julia> crs = metadata(df, "GEOINTERFACE:crs");

julia> jsonstr = JSON3.write(GeoFormatTypes.val(crs));

julia> newcrs = ProjJSON(jsonstr);

julia> GeoParquet.write("test.parquet", df, (:geometry,), newcrs)
"test.parquet"

julia> GeoParquet.read("test.parquet")
ERROR: ArgumentError: Not a ProjJSON: ...

julia> ds = Parquet2.Dataset("test.parquet");

julia> meta = JSON3.read(Parquet2.metadata(ds)["geo"]);

julia> meta.columns.geometry.crs
JSON3.Object{Base.CodeUnits{UInt8, String}, SubArray{UInt64, 1, Vector{UInt64}, Tuple{UnitRange{Int64}}, true}} with 1318 entries:
  Symbol("1") => "{"
  Symbol("2") => "\""
  Symbol("3") => "\$"
  Symbol("4") => "s"
  Symbol("5") => "c"
  ⋮           => ⋮

[rafaqz]

Looks like a bug

[eliascarv]

This happens because the GeoParquet.jl implementation treats ProjJSON as a dictionary:

Unfortunately, I don't know what the motivations for this implementation were.

[rafaqz]

That's also type piracy!

[eliascarv]

Yes, my PR doesn't solve these issues, but for now, I think it's enough. These issues can be solved in other PRs.
What do you think?

[asinghvi17]

Looks good to me for now, would be nice to add a test though. Maybe the code you have in the README would suffice for that?

Long term we need better geometry support, since WKB geoms won't have attached CRS for example. But that can wait for later.

[eliascarv]

@asinghvi17, tests added.

[evetion]

Thanks @eliascarv, sorry for the delay in merging. I will do some light maintenance here and make a release soon.