Prepares for v2.0 using the new OTP-27 `json` module

[williamthome]

Closes #36

This PR prepares Euneus for a new major release using the new OTP-27 json module.

The code below is just a copy-paste. More info is coming soon.

Basic Usage

1> JSON = euneus:encode(#{title => <<"The Movie">>, year => 1990, starring => ['Mike', <<"Joe">>, "Robert"]}).
<<"{\"title\":\"The Movie\",\"year\":1990,\"starring\":[\"Mike\",\"Joe\",[82,111,98,101,114,116]]}">>
2> euneus:decode(JSON).
#{<<"starring">> => [<<"Mike">>,<<"Joe">>,"Robert"],
  <<"title">> => <<"The Movie">>,<<"year">> => 1990}

Encode

-type encode() :: fun((term()) -> iodata()).
-type encode_callback(Type) :: fun((Type, encode(), #state{}) -> iodata()).
-type codec(Type) :: fun((Type) -> iodata()).
-type atom_codec() :: codec(atom()).
-type binary_codec() :: codec(binary()).
-type integer_codec() :: codec(integer()).
-type float_codec() :: codec(float()).
-type list_codec() :: proplist
                    | {proplist, IsProplist :: fun((list()) -> boolean())}
                    | codec(list()).
-type map_codec() :: drop_nulls | codec(map()) | [codec(map())].
-type tuple_codec() :: datetime
                     | timestamp
                     | ipv4
                     | ipv6
                     | {records, [{Name :: atom(), Fields :: [atom()]}]}
                     | codec(tuple()).
-type pid_codec() :: codec(pid()).
-type port_codec() :: codec(port()).
-type reference_codec() :: codec(reference()).
-type options() :: #{ escape => fun((binary()) -> iodata())
                    , nulls => [term()]
                    , sort_keys => boolean()
                    , atom => atom_codec() | [atom_codec()]
                    , binary => binary_codec() | [binary_codec()]
                    , integer => integer_codec() | [integer_codec()]
                    , float => float_codec() | [float_codec()]
                    , list => list_codec() | [list_codec()]
                    , map => map_codec() | [map_codec()]
                    , tuple => tuple_codec() | [tuple_codec()]
                    , pid => pid_codec() | [pid_codec()]
                    , port => port_codec() | [port_codec()]
                    , reference => reference_codec() | [reference_codec()]
                    , encode_atom => encode_callback(atom())
                    , encode_binary => encode_callback(binary())
                    , encode_integer => encode_callback(integer())
                    , encode_float => encode_callback(float())
                    , encode_list => encode_callback(list())
                    , encode_map => encode_callback(map())
                    , encode_tuple => encode_callback(tuple())
                    , encode_pid => encode_callback(pid())
                    , encode_port => encode_callback(port())
                    , encode_reference => encode_callback(reference())
                    , integer_to_binary => fun((integer()) -> binary())
                    , float_to_binary => fun((float()) -> binary())
                    }.

Decode

-type codec(Type) :: fun((Type) -> term()).
-type array_finish_fun() :: fun((list(), list()) -> {term(), list()}).
-type object_finish_fun() :: fun((proplist(), proplist()) -> {term(), proplist()}).
-type proplist() :: proplists:proplist().
-type array_codec() :: codec(list()).
-type object_codec() :: codec(map()).
-type key_codec() :: datetime
                   | timestamp
                   | inet
                   | ipv4
                   | ipv6
                   | pid
                   | port
                   | reference
                   | copy
                   | atom
                   | existing_atom
                   | integer
                   | {integer, Base :: 2..36}
                   | float
                   | list
                   | codec(binary()).
-type value_codec() :: datetime
                     | timestamp
                     | inet
                     | ipv4
                     | ipv6
                     | pid
                     | port
                     | reference
                     | copy
                     | atom
                     | existing_atom
                     | integer
                     | {integer, Base :: 2..36}
                     | float
                     | list
                     | codec(binary()).
-type options() :: #{ null => term()
                    , array => array_codec() | [array_codec()]
                    , object => object_codec() | [object_codec()]
                    , key => key_codec() | [key_codec()]
                    , value => value_codec() | [value_codec()]
                    , array_finish => ordered
                                    | reversed
                                    | array_finish_fun()
                    , object_finish => map
                                     | proplist
                                     | reversed_proplist
                                     | object_finish_fun()
                    , binary_to_integer => fun((binary()) -> integer())
                    , binary_to_float => fun((binary()) -> float())
                    }.

[williamthome]

Closing in favor of https://github.com/williamthome/euneus/pull/53.