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1. Verify the validity of access token

   1. Return 401 in case validation fails

2. Check user scopes in order to perform this action (scope = 'preperson:createwrite')

   1. Return 403 in case invalid scope(s)

...

1. Check external_id is not empty.

   1. In case of error - return 422 (external_id should not be empty)

2. Check external_id is unique ? (unique within le?)

   1. In case of error - return 422 (external_id already exists) ?

Generate person_id

1. Generate person_id (will be returned in response). Ensure there is no such person_id in MPI.persons

2. Generate patient_id to save it in patients collection.

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