So I'm trying to change a specific user's contents using patch, right here:

const mutations =  [
        {
          patch: {
            query: "*[_type == 'user']",
            set: {
                email: email,
                username: username,
                photo: photo
            }
          }
        }
      ]

    await fetch(`https://${process.env.SANITY_PROJECT_ID}.api.sanity.io/v2021-06-07/data/mutate/production`, {
        headers: {
          'Content-type': 'application/json',
           Authorization: `Bearer ${tokenWithWriteAccess}` // Yes the token does exist in an constant variable that is not shown here.
        },
            body: JSON.stringify({mutations}),
            method: 'POST'
    });

Not sure if I'm doing the mutations right but basically I want to change the user's username,email and photo for a specific doc.I just want to know that can I use other fields like username or email for fetching and patching the docs?

Any help will be appreciated.