Document where the nodeID is stored

[physikerwelt]

When a version of the docker container will be use deployed the old nodeid vanishes (only the /data folder is persistent). If we aim for persistent nodeIds we would want to document where those ids are stored (together with other state) that might be reused after the docker container was replaced with a new version.

[ihlec]

7.1 Node Identity & Key Storage

A node's Peer ID is derived from its Ed25519 private key. This key is used for all message signing, libp2p authentication, and shard assignment. The key is resolved at startup in the following order:

Priority	Source	When used	Storage location
1	IPFS repo	IPFS_PATH is set and repo is accessible	$IPFS_PATH/config (Identity.PrivKey)
2	Persistent key file	IPFS_PATH unset or repo inaccessible	DLOCKSS_IDENTITY_PATH (default: {DLOCKSS_DATA_DIR}/../dlockss.key)
3	Auto-generated	No existing key found	Saved to the path from priority 2