Create alias for PAtient, Case, Specimen and Blood items for external use

[Nicklas Nordborg]

The SCAN-B ID that is used to keep track of all items is sensitive information that we should avoid to use externally. We should add a new unique identifier to Patient, Case, Specimen, NoSpecimen and Blood (including fullow-up blood) items. A simple running number that is zero-padded to 6 digits should be ok (same as we currently do for naming Patient items). Use 'P' as prefix for Patients, 'C' as prefix for Case items, and 'S' as prefix for specimen/nospecimen and 'B' for blood. If a case is arriving with multiple tubes, each tube should have it's own unique identifier.

The new identifier should be saved in the "External ID" field.

Other tools can then use the external identifiers instead of the SCAN-B ids. For example:

1234567.1.l.r.lib --> P000001.C000001.S000001.l.r.lib

Other notes:

• Since we are already using a similar scheme for the 'name' of Patients, the we should create random gaps in the external id sequence. For example by randomly incrementing with 2 instead of 1.
• Cases that are created as placeholder for retracted items should not have en external id.