rather than using the `normalise_phone_number` function, use the
`validate_and_format_phone_number` function - this will also convert
all numbers to international format, which means we won't need to
worry about whether the user enters internaional or UK phone numbers
when searching
two endpoints:
* get all inbound sms for a service (you can limit to the X most
recent, or filter by user's phone number [which will be normalised])
* get a summary of inbound sms for a service - returns the count of
inbound sms in the database, and the date that the most recent was
sent
