`ProjectTo` is too permissive?

Maybe this should be an error?

julia> using AxisKeys

julia> ka = wrapdims(rand(3, 2), obs=1:3, point=["a", "b"]);

julia> kb = wrapdims(rand(3, 2), obs=1:3, point=["c", "d"]);

julia> ProjectTo(ka)(kb)
2-dimensional KeyedArray(NamedDimsArray(...)) with keys:
↓   obs ∈ 3-element UnitRange{Int64}
→   point ∈ 2-element Vector{String}
And data, 3×2 Matrix{Float64}:
      ("a")      ("b")
 (1)   0.928905   0.705413
 (2)   0.493408   0.997449
 (3)   0.877819   0.816695

We probably want to think about similar things as in https://github.com/invenia/NamedDims.jl/pull/201#issuecomment-1201180921

Start by reproducing the shown ProjectTo(ka)(kb) example and read the ProjectTo entry point. Review the referenced NamedDims.jl discussion to determine when mismatched keys should raise an error, then define the intended behavior and add coverage for the agreed cases.