Validate `firstEvaluatedKey` and `lastEvaluatedKey`'s length

[majecty]

Here is the code that validates firstEvaluatedKey and lastEvaluatedKey.

export const txPaginationSchema = {
    firstEvaluatedKey: Joi.array().items(Joi.number(), Joi.number()),
    lastEvaluatedKey: Joi.array().items(Joi.number(), Joi.number())
};

The above condition does not check an input array's length. All of these inputs [], [1], [1,2] and [1,2,3] are valid in the current implementation. Only [1,2] should pass the validation and other [], [1], [1,2,3] should fail the validation.