feat: freeze v1 transport contracts (#4)

Closes #4

src/FinalFactory.Rendezvous.Contracts/Identifiers/StringIdentifierJsonConverter.cs

@@ -0,0 +1,37 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace FinalFactory.Rendezvous.Contracts;
+
+internal abstract class StringIdentifierJsonConverter<TIdentifier> : JsonConverter<TIdentifier>
+{
+    public sealed override TIdentifier Read(
+        ref Utf8JsonReader reader,
+        Type typeToConvert,
+        JsonSerializerOptions options)
+    {
+        if (reader.TokenType != JsonTokenType.String)
+        {
+            throw new JsonException($"{typeof(TIdentifier).Name} must be a JSON string.");
+        }
+
+        string value = reader.GetString() ?? string.Empty;
+
+        try
+        {
+            return Parse(value);
+        }
+        catch (Exception exception) when (exception is ArgumentException or FormatException)
+        {
+            throw new JsonException($"Invalid {typeof(TIdentifier).Name}.", exception);
+        }
+    }
+
+    public sealed override void Write(
+        Utf8JsonWriter writer,
+        TIdentifier value,
+        JsonSerializerOptions options) => writer.WriteStringValue(Format(value));
+
+    protected abstract TIdentifier Parse(string value);
+    protected abstract string Format(TIdentifier value);
+}