Add test cases:
  show that a unique index on the partitioning key gets no warning.
  show that a unique compound index on the partitioning key and another column gets no warning.
  show that a unique index on the partitioning key and an expression like abs(age) gets no warning.
  show that a unique index on an expression of the partitioning key like substr(1, 2, name) gets a warning.
  show that a unique index on an unrelated expression like abs(age) gets a warning.