Prisma

I'm trying to create a relation in my database. I've got a datamodel that looks like this (simplified);
```
type CheckIn {
  id: ID! @unique
  location: Location!
  user: User!
}

type User {
  id: ID! @unique
  checkIns: [CheckIn!]
}

type Location {
  id: ID! @unique
  checkIns: [CheckIn!]
}
```

How can I add `@relation` directives to finish the relationship? Each `CheckIn` has a user and a location, and each `User` and `Location` has a list of `CheckIn`s that refer to it.

And, related question, I don't have a manual way of creating new `Location` entries, but I want to pass in location data when I create a new `CheckIn`. What's the right way to do that?

This is how I'm creating the `CheckIn`, but I don't know what to pass in for `location`;
```
async createCheckIn(parent, { title, location }, context) {
    const userId = getUserId(context);
    return context.prisma.createCheckIn({
      title,
      location,
      public: true,
      user: { connect: { id: userId } }
    });
  }
```