Add custom type map

[p14n]

Added custom type map by passing in opts as second param to schema (i.e. {:custom-type-map {"DateTime" 'DateTime}} )

[luchiniatwork]

Hey @p14n ... this seems to be a feature that is clearly missing.

What do you think of something similar to the approach that was taken on the Datomic interface? See https://github.com/hodur-org/hodur-datomic-schema#scalar-types-and-finer-grained-control

[tothda]

Hey @luchiniatwork !

I also need custom scalar support. I could work on this feature if we can agree on the interface.

How about this?

  (deftest test-custom-scalars
           (let [s (schema->lacinia '[^{:lacinia/tag true}
                                      default

                                      ^{:lacinia/scalar true
                                        :lacinia/parse :date-time-parser
                                        :lacinia/serialize :date-time-serializer}
                                      DateTime []

                                      Person
                                      [^ID id
                                       ^DateTime dob]])]

             (is (= '{:scalars
                      {:DateTime
                       {:parse :date-time-parser
                        :serialize :date-time-serializer}}
                      :objects
                      {:Person
                       {:fields
                        {:id {:type (non-null ID)}
                         :dob {:type (non-null :DateTime)}}}
                       }
                      }
                    s))))