Add columns on contacts table

[Tom Smith]

Task

We require DB migrations on the contacts table by adding the following columns:

UserContact

• scid: short channel id / string
• index: contact index / integer
• contactRouteHint: route hint of the contactKey (format: IspPubkey_scid) / string
• childPubKey: child pub key for each contact / string

Acceptance Criteria

• New columns for scid, index, contactRouteHint, childPubKey