How do we do this in EOSIO multi_index table? Want to define a table with an auto increment primary key id.
Have a look to available_primary_key in the EOS documentation, multi indexes do support auto increment keys.
You check the way monstereos did. They have table st_pet_config define last_id start with 0 and everytime you create new pet last_id increase https://github.com/leordev/monstereos/blob/master/contracts/pet/pet.hpp#L85