[chores] Use settings to show choices in model fields

Signed-off-by: Gagan Deep <[email protected]>

Author: pandafy

openwisp_controller/config/migrations/0001_squashed_0002_config_settings_uuid.py

@@ -46,10 +46,7 @@ class Migration(migrations.Migration):
                 (
                     'backend',
                     models.CharField(
-                        choices=[
-                            ('netjsonconfig.OpenWrt', 'OpenWRT'),
-                            ('netjsonconfig.OpenWisp', 'OpenWISP Firmware 1.x'),
-                        ],
+                        choices=app_settings.BACKENDS,
                         help_text=(
                             'Select <a href="http://netjsonconfig.openwisp.org'
                             '/en/stable/" target="_blank">netjsonconfig</a> '
@@ -242,10 +239,7 @@ class Migration(migrations.Migration):
                 (
                     'backend',
                     models.CharField(
-                        choices=[
-                            ('netjsonconfig.OpenWrt', 'OpenWRT'),
-                            ('netjsonconfig.OpenWisp', 'OpenWISP Firmware 1.x'),
-                        ],
+                        choices=app_settings.BACKENDS,
                         help_text=(
                             'Select <a href="http://netjsonconfig.openwisp.org'
                             '/en/stable/" target="_blank">netjsonconfig</a> backend'

tests/openwisp2/sample_config/migrations/0001_initial.py

@@ -64,10 +64,7 @@ class Migration(migrations.Migration):
                 (
                     'backend',
                     models.CharField(
-                        choices=[
-                            ('netjsonconfig.OpenWrt', 'OpenWRT'),
-                            ('netjsonconfig.OpenWisp', 'OpenWISP Firmware 1.x'),
-                        ],
+                        choices=app_settings.BACKENDS,
                         help_text=(
                             'Select <a href="http://netjsonconfig.openwisp.org/en/'
                             'stable/" target="_blank">netjsonconfig</a> backend'
@@ -491,10 +488,7 @@ class Migration(migrations.Migration):
                 (
                     'backend',
                     models.CharField(
-                        choices=[
-                            ('netjsonconfig.OpenWrt', 'OpenWRT'),
-                            ('netjsonconfig.OpenWisp', 'OpenWISP Firmware 1.x'),
-                        ],
+                        choices=app_settings.BACKENDS,
                         help_text=(
                             'Select <a href="http://netjsonconfig.openwisp.org/en/'
                             'stable/" target="_blank">netjsonconfig</a> backend'