Implements a custom `Encoder` that maps native Swift types (String, Int, Double, Bool, Date, Dictionary, Array, Optional) into DynamoDB's `AttributeValue` representation. Supports configurable date encoding strategies (secondsSince1970, millisecondsSince1970, iso8601, deferred to timestamp, custom). The encoder handles nested collections and recursive structures, and is designed to be used directly with DynamoDB put/update operations. This component is self-contained, requiring only SotoCore types, and can be extracted for any Swift project needing DynamoDB serialization.

Provides the reverse operation of `DynamoDBEncoder`: a custom `Decoder` that converts DynamoDB's `AttributeValue` map (`[String: AttributeValue]`) back into Swift types. It handles all DynamoDB types (S, N, B, BOOL, NULL, M, L, SS, NS, BS) and supports the same date decoding strategies. Uses recursive keyed, unkeyed, and single-value decoding containers. This component is critical for reading data from DynamoDB and mapping it to domain models, and is reusable in any Swift project using DynamoDB's document model.

Generates presigned POST policies for direct browser uploads to S3. Computes HMAC-SHA256 signatures, creates base64-encoded policy documents with expiration and conditions, and returns the complete form fields required for POST uploads. Demonstrates advanced usage of AWS Signature V4 and credential scoping. The component is standalone and can be reused in any Swift application that needs to allow client-side uploads to S3 without exposing permanent credentials.