+/**
+ * Returns a list of matches found between the beacons and diagnoses.
+ *
+ * This searches through the list of DTKs and the list of RPIs provided, and
+ * returns a list of matches.
+ *
+ * If the returned list has any elements in, this would suggest that the user
+ * has been in contact with someone who tested positive and uploaded their DTK
+ * to a Diagnosis Server.
+ *
+ * The match list isn't cleared by this call and so any new values will be
+ * appended to it.
+ *
+ * @param data The list that any matches will be appended to.
+ * @param beacons A list of RPIs extracted from overheard BLE beacons.
+ * @param diagnosis_keys A list of DTKs downloaed from a Diagnosis Server.
+ */