Move regex to validators.py

A gateway should be an interface like any other IP.
Use tag to identify it.

It shouldn't be possible to change the ICS id of an item.
But when registering a bunch of existing items via the API, we need to
allocate an ics_id otherwise not much can be done in the interface.
The id is required for the view and edit page.

The solution is to define some "temporary" ids that don't correspond to
any pre-printed labels.
Items with a temporary id can be assigned a real ics_id when assigning a
label.

Reserved ids start with 'ZZ' (from ZZA000 to ZZZ999)

ICS id can now be non nullable.

Description shall be filled at the host level

See http://docs.sqlalchemy.org/en/latest/core/compiler.html#utc-timestamp-function

TODO: we should be able to render HTML in the comments
Look at https://github.com/miguelgrinberg/Flask-PageDown

- Rename Host to Interface
- Create new Host table to group interfaces

There is no point displaying the LDAP groups in the profile

- All created tokens are stored in the database.
  To revoke a token, we just delete it from the database.
  Tokens not found in the database are thus considered unvalid / revoked.

- Add button to copy generated token to the clipboard

- Redesign profile page

hosttags table required for the many-to-many relationship
See http://flask-sqlalchemy.pocoo.org/2.3/models/#many-to-many-relationships

- Several IPs (hosts) can be associated to one MAC address
- Host name shall be non nullable

- refactor Network class

- network name should be unique and not nullable
- force all name fields to StringField

Don't ovveride SQLAlchemy __init__ method on db.Model classes.

See http://flask-sqlalchemy.pocoo.org/2.3/quickstart/:
SQLAlchemy adds an implicit constructor to all model classes which
accepts keyword arguments for all its columns and relationships. If you
decide to override the constructor for any reason, make sure to keep
accepting **kwargs and call the super constructor with those **kwargs to
preserve this behavior

ValidationError is catched by default by flask-admin.
It's easy to catch in the api/main.py to raise a CSEntryError.

We actually don't need to catch ValidationError as it's based on
ValueError that we already catch.

The database constraints will catch the same error
(and raise an IntegrityError).

Having some validation at the model level allows to display nicer error
messages.
We use CSEntryError exception and not ValidationError so that it can be
used both by the API and views.

- A network defines an available range of IP addresses
- A host defines an IP address and name
- A host is always linked to a network
- A mac address is always linked to an item (physical equipment)
- A mac address can be linked to one host (IP)
- An item can have several mac addresses

Text is as efficient in Postgres and is recommended over varchar.
It avoids having to put an arbitrary max length to strings.

CSE makes it clearer that it's linked to CSEntry

ics_id, serial_number, manufacturer_id and model_id should not change.
Repeating them in the history table takes space for nothing.

We are only interested in tracking the status, location and parent.

Pass ?qrcode=true as query string

- add more tests
- patching an item update children location and status
- setting the parent on an item updates the location and status with the
  parent ones

The serial number might not be unique and can't be used
as the string to hash.
There are for example SD cards that all have the same SN.

Using an ICS id allows to pre-print labels that can be assigned to
hardware when scanning serial numbers.
This id shall be easy to remember (unlike UUID).

Most items won't have a name.
hostname could be added in a separate table if required.

The citext module provides a case-insensitive character string type.
Use CIText for QRCodeMixin name column.
name should be case-insensitive to avoid duplicate names.