Update input validation tests to assert against specific error

[ashley-evans]

Value added

Future changes to the input schema will fail for appropriate reasons

Description

Currently the tests for each lambda's input schema only check whether the input fails validation. However, they do not check if the input failed validation for the right reason.

This means that potentially some tests are failing for the wrong reason.

Acceptance Criteria

AC01

• Update input validation tests for each lambda to assert against a specific JSON schema validation error