Add support for configuring properties as Headers with the model builder's FLUENT API

[tomasfabian]

Add support for marking columns as Headers with the model builder.

The proposed API is as follows:

ModelBuilder modelBuilder = new();

modelBuilder.Entity<Item>()
  .Property(b => b.Description)
  .WithHeaders();

CREATE STREAM item (
    Description ARRAY<STRUCT<key STRING, value BYTES>> HEADERS
) WITH (
    kafka_topic = 's3',
    value_format = 'json'
);

or for a single HEADER the type must be of type []byte:

ModelBuilder modelBuilder = new();

modelBuilder.Entity<Item>()
  .Property(b => b.Description)
  .WithHeader("abc");

CREATE STREAM item (
    Description BYTES HEADER('abc')
) WITH (
    kafka_topic = 's4',
    value_format = 'json'
);

[tomasfabian]

Was released in:

dotnet add package ksqlDb.RestApi.Client --version 5.1.0