Draft a technical specification document (similar to an RFC) for a RESTful API interface that manages file storage across a decentralized network (like IPFS but with a custom consensus layer). Define the JSON schema for upload requests, including sharding parameters, redundancy factors, and encryption metadata. Specify the handshake protocol for node discovery and the mechanism for retrieving file integrity proofs (Merkle trees). Additionally, define the error codes for network failure scenarios such as 'insufficient node availability' or 'data corruption detected'.