Support "updateMany" model method

[mswjs]

Support "updateMany" model method

[kettanaito]

With updateMany it may be useful for the data property to support an evolution of values: accept a previous value of a given entity and evolve it into the next value.

db.user.updateMany({
  which: { id: { in: [1, 2, 3] } },
  data: {
    // Evolve each individual `firstName` value.
    firstName: value => value.toUpperCase()
  }
})