Update schema.sql

[Skaleras]

added primary key id to ingredient table, it blew up in my computer not being able to parse the sql

[dainank]

You can also add it on a single line, not sure what is neater/clearer:

create table if not exists Ingredient (
  id varchar(4) primary key not null,
  name varchar(25) not null,
  type varchar(10) not null
);

[nickolayl]

or you can use unique

create table if not exists Ingredient (
    id varchar(4) unique not null,
    name varchar(25) not null,
    type varchar(10) not null
);