"auth-method": "did" for mainnet

**Describe the bug**

In the daemon-config.json file, `anchor` section, `auth-method": "did"` is required for mainnet.

Anchoring will fail if the `network.name` and `node.privateSeedUrl` are correct but the `anchor` setting is missing.

This value should default to `auth-method": "did"` for mainnet since it's controlled by the CAS endpoint defined by the network name.

Start by locating the daemon-config.json handling for the anchor section and how network.name selects mainnet behavior. Check the handling of node.privateSeedUrl and the auth-method value, then verify that mainnet defaults to did and anchoring works when the other settings are correct.

Written by the indexing model from the issue text.