Initialize CBDD solution and add a .NET-focused gitignore for generated artifacts.

src/CBDD.Core/Collections/BaseMappers.cs

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+using System;
+using System.Buffers;
+using ZB.MOM.WW.CBDD.Bson;
+using ZB.MOM.WW.CBDD.Core.Indexing;
+using System.Linq;
+using System.Collections.Generic;
+using ZB.MOM.WW.CBDD.Bson.Schema;
+
+namespace ZB.MOM.WW.CBDD.Core.Collections;
+
+/// <summary>
+/// Base class for custom mappers that provides bidirectional IndexKey mapping for standard types.
+/// </summary>
+public abstract class DocumentMapperBase<TId, T> : IDocumentMapper<TId, T> where T : class
+{
+    /// <summary>
+    /// Gets the target collection name for the mapped entity type.
+    /// </summary>
+    public abstract string CollectionName { get; }
+
+    /// <summary>
+    /// Serializes an entity instance into BSON.
+    /// </summary>
+    /// <param name="entity">The entity to serialize.</param>
+    /// <param name="writer">The BSON writer to write into.</param>
+    /// <returns>The number of bytes written.</returns>
+    public abstract int Serialize(T entity, BsonSpanWriter writer);
+
+    /// <summary>
+    /// Deserializes an entity instance from BSON.
+    /// </summary>
+    /// <param name="reader">The BSON reader to read from.</param>
+    /// <returns>The deserialized entity.</returns>
+    public abstract T Deserialize(BsonSpanReader reader);
+
+    /// <summary>
+    /// Gets the identifier value from an entity.
+    /// </summary>
+    /// <param name="entity">The entity to read the identifier from.</param>
+    /// <returns>The identifier value.</returns>
+    public abstract TId GetId(T entity);
+
+    /// <summary>
+    /// Sets the identifier value on an entity.
+    /// </summary>
+    /// <param name="entity">The entity to update.</param>
+    /// <param name="id">The identifier value to assign.</param>
+    public abstract void SetId(T entity, TId id);
+
+    /// <summary>
+    /// Converts a typed identifier value into an index key.
+    /// </summary>
+    /// <param name="id">The identifier value.</param>
+    /// <returns>The index key representation of the identifier.</returns>
+    public virtual IndexKey ToIndexKey(TId id) => IndexKey.Create(id);
+
+    /// <summary>
+    /// Converts an index key back into a typed identifier value.
+    /// </summary>
+    /// <param name="key">The index key to convert.</param>
+    /// <returns>The typed identifier value.</returns>
+    public virtual TId FromIndexKey(IndexKey key) => key.As<TId>();
+
+    /// <summary>
+    /// Gets all mapped field keys used by this mapper.
+    /// </summary>
+    public virtual IEnumerable<string> UsedKeys => GetSchema().GetAllKeys();
+
+    /// <summary>
+    /// Builds the BSON schema for the mapped entity type.
+    /// </summary>
+    /// <returns>The generated BSON schema.</returns>
+    public virtual BsonSchema GetSchema() => BsonSchemaGenerator.FromType<T>();
+}
+
+/// <summary>
+/// Base class for mappers using ObjectId as primary key.
+/// </summary>
+public abstract class ObjectIdMapperBase<T> : DocumentMapperBase<ObjectId, T>, IDocumentMapper<T> where T : class
+{
+    /// <inheritdoc />
+    public override IndexKey ToIndexKey(ObjectId id) => IndexKey.Create(id);
+
+    /// <inheritdoc />
+    public override ObjectId FromIndexKey(IndexKey key) => key.As<ObjectId>();
+}
+
+/// <summary>
+/// Base class for mappers using Int32 as primary key.
+/// </summary>
+public abstract class Int32MapperBase<T> : DocumentMapperBase<int, T> where T : class
+{
+    /// <inheritdoc />
+    public override IndexKey ToIndexKey(int id) => IndexKey.Create(id);
+
+    /// <inheritdoc />
+    public override int FromIndexKey(IndexKey key) => key.As<int>();
+}
+
+/// <summary>
+/// Base class for mappers using String as primary key.
+/// </summary>
+public abstract class StringMapperBase<T> : DocumentMapperBase<string, T> where T : class
+{
+    /// <inheritdoc />
+    public override IndexKey ToIndexKey(string id) => IndexKey.Create(id);
+
+    /// <inheritdoc />
+    public override string FromIndexKey(IndexKey key) => key.As<string>();
+}
+
+/// <summary>
+/// Base class for mappers using Guid as primary key.
+/// </summary>
+public abstract class GuidMapperBase<T> : DocumentMapperBase<Guid, T> where T : class
+{
+    /// <inheritdoc />
+    public override IndexKey ToIndexKey(Guid id) => IndexKey.Create(id);
+
+    /// <inheritdoc />
+    public override Guid FromIndexKey(IndexKey key) => key.As<Guid>();
+}