Closes #8550: Implement ASN ranges (#11835)

* Move ASN to a separate module

* Move ASNField from dcim to ipam

* Introduce ASNRange model

* Add relationship from ASN to ASNRange

* Add an available-asns API endpoint

* Add RIR assignment for ASNRange

* Add standard tests

* Move child ASNs to a tabbed view

* Remove FK on ASN to ASNRange

* Add tests for provisioning available ASNs

* Add docs for ASNRange

netbox/ipam/fields.py

@@ -1,10 +1,21 @@
 from django.core.exceptions import ValidationError
+from django.core.validators import MinValueValidator, MaxValueValidator
 from django.db import models
 from netaddr import AddrFormatError, IPNetwork
 
 from . import lookups, validators
 from .formfields import IPNetworkFormField
 
+__all__ = (
+    'ASNField',
+    'IPAddressField',
+    'IPNetworkField',
+)
+
+# BGP ASN bounds
+BGP_ASN_MIN = 1
+BGP_ASN_MAX = 2**32 - 1
+
 
 class BaseIPField(models.Field):
 
@@ -93,3 +104,19 @@ IPAddressField.register_lookup(lookups.NetIn)
 IPAddressField.register_lookup(lookups.NetHostContained)
 IPAddressField.register_lookup(lookups.NetFamily)
 IPAddressField.register_lookup(lookups.NetMaskLength)
+
+
+class ASNField(models.BigIntegerField):
+    description = "32-bit ASN field"
+    default_validators = [
+        MinValueValidator(BGP_ASN_MIN),
+        MaxValueValidator(BGP_ASN_MAX),
+    ]
+
+    def formfield(self, **kwargs):
+        defaults = {
+            'min_value': BGP_ASN_MIN,
+            'max_value': BGP_ASN_MAX,
+        }
+        defaults.update(**kwargs)
+        return super().formfield(**defaults)