Metadata for primitive collection mapping

Part of #30730

Some stuff remaining, but wanted to get this out there for initial review.

Missing:
- ElementType in compiled model
- Negative cases
- More tests

Review updates

Change builder shape based on API review

Updated based on review.

More tests and refactoring of how ElementTypes are created.

src/EFCore.Cosmos/Extensions/CosmosPrimitiveCollectionBuilderExtensions.cs

@@ -0,0 +1,91 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.EntityFrameworkCore.Cosmos.Metadata.Internal;
+
+namespace Microsoft.EntityFrameworkCore;
+
+/// <summary>
+///     Cosmos-specific extension methods for <see cref="PrimitiveCollectionBuilder" />.
+/// </summary>
+/// <remarks>
+///     See <see href="https://aka.ms/efcore-docs-modeling">Modeling entity types and relationships</see>, and
+///     <see href="https://aka.ms/efcore-docs-cosmos">Accessing Azure Cosmos DB with EF Core</see> for more information and examples.
+/// </remarks>
+public static class CosmosPrimitiveCollectionBuilderExtensions
+{
+    /// <summary>
+    ///     Configures the property name that the property is mapped to when targeting Azure Cosmos.
+    /// </summary>
+    /// <remarks>
+    ///     <para>
+    ///         If an empty string is supplied, the property will not be persisted.
+    ///     </para>
+    ///     <para>
+    ///         See <see href="https://aka.ms/efcore-docs-modeling">Modeling entity types and relationships</see>, and
+    ///         <see href="https://aka.ms/efcore-docs-cosmos">Accessing Azure Cosmos DB with EF Core</see> for more information and examples.
+    ///     </para>
+    /// </remarks>
+    /// <param name="primitiveCollectionBuilder">The builder for the property being configured.</param>
+    /// <param name="name">The name of the property.</param>
+    /// <returns>The same builder instance so that multiple calls can be chained.</returns>
+    public static PrimitiveCollectionBuilder ToJsonProperty(
+        this PrimitiveCollectionBuilder primitiveCollectionBuilder,
+        string name)
+    {
+        Check.NotNull(name, nameof(name));
+
+        primitiveCollectionBuilder.Metadata.SetJsonPropertyName(name);
+
+        return primitiveCollectionBuilder;
+    }
+
+    /// <summary>
+    ///     Configures the property name that the property is mapped to when targeting Azure Cosmos.
+    /// </summary>
+    /// <remarks>
+    ///     See <see href="https://aka.ms/efcore-docs-modeling">Modeling entity types and relationships</see>, and
+    ///     <see href="https://aka.ms/efcore-docs-cosmos">Accessing Azure Cosmos DB with EF Core</see> for more information and examples.
+    /// </remarks>
+    /// <typeparam name="TProperty">The type of the property being configured.</typeparam>
+    /// <param name="primitiveCollectionBuilder">The builder for the property being configured.</param>
+    /// <param name="name">The name of the property.</param>
+    /// <returns>The same builder instance so that multiple calls can be chained.</returns>
+    public static PrimitiveCollectionBuilder<TProperty> ToJsonProperty<TProperty>(
+        this PrimitiveCollectionBuilder<TProperty> primitiveCollectionBuilder,
+        string name)
+        => (PrimitiveCollectionBuilder<TProperty>)ToJsonProperty((PrimitiveCollectionBuilder)primitiveCollectionBuilder, name);
+
+    /// <summary>
+    ///     Configures this property to be the etag concurrency token.
+    /// </summary>
+    /// <remarks>
+    ///     See <see href="https://aka.ms/efcore-docs-modeling">Modeling entity types and relationships</see>, and
+    ///     <see href="https://aka.ms/efcore-docs-cosmos">Accessing Azure Cosmos DB with EF Core</see> for more information and examples.
+    /// </remarks>
+    /// <param name="primitiveCollectionBuilder">The builder for the property being configured.</param>
+    /// <returns>The same builder instance so that multiple calls can be chained.</returns>
+    public static PrimitiveCollectionBuilder IsETagConcurrency(this PrimitiveCollectionBuilder primitiveCollectionBuilder)
+    {
+        primitiveCollectionBuilder
+            .IsConcurrencyToken()
+            .ToJsonProperty("_etag")
+            .ValueGeneratedOnAddOrUpdate();
+
+        return primitiveCollectionBuilder;
+    }
+
+    /// <summary>
+    ///     Configures this property to be the etag concurrency token.
+    /// </summary>
+    /// <remarks>
+    ///     See <see href="https://aka.ms/efcore-docs-modeling">Modeling entity types and relationships</see>, and
+    ///     <see href="https://aka.ms/efcore-docs-cosmos">Accessing Azure Cosmos DB with EF Core</see> for more information and examples.
+    /// </remarks>
+    /// <typeparam name="TProperty">The type of the property being configured.</typeparam>
+    /// <param name="primitiveCollectionBuilder">The builder for the property being configured.</param>
+    /// <returns>The same builder instance so that multiple calls can be chained.</returns>
+    public static PrimitiveCollectionBuilder<TProperty> IsETagConcurrency<TProperty>(
+        this PrimitiveCollectionBuilder<TProperty> primitiveCollectionBuilder)
+        => (PrimitiveCollectionBuilder<TProperty>)IsETagConcurrency((PrimitiveCollectionBuilder)primitiveCollectionBuilder);
+}