feat(db+indexer+gql): idty_by_username

db/src/lib.rs

db/src/values/gva_idty_db.rs

dbs-reader/src/lib.rs

dbs-reader/src/uds_of_pubkey.rs

gql/src/entities/idty_gva.rs

gql/src/queries/idty.rs

gql/src/queries/wallets.rs

indexer/src/identities.rs

indexer/src/lib.rs