Add uniquenessand length validators to serializer fields.

Move username regex validator from model to serializer, since the model validation
does not run automatically on model save:
https://docs.djangoproject.com/en/dev/ref/validators/#how-validators-are-run

Note: For the importer and publisher uniqueness validator to take effect they must
be declared on the Plugin importer and publisher class like so:

Class PluginPublisherSerializer(pulpcore.plugin.serializers.PublisherSerializer):
    class Meta:
        validators = PublisherSerializer.Meta.validators

closes #2984
https://pulp.plan.io/issues/2984

platform/pulpcore/app/models/auth.py

@@ -9,7 +9,6 @@
 from gettext import gettext as _
 
 from django.contrib.auth.models import AbstractBaseUser, BaseUserManager, PermissionsMixin
-from django.core import validators
 from django.db import models
 
 
@@ -56,13 +55,6 @@ class User(AbstractBaseUser, PermissionsMixin):
         verbose_name=_('username'),
         max_length=150,
         unique=True,
-        validators=[
-            validators.RegexValidator(
-                r'^[\w.@+-]+$',
-                _('Enter a valid username. This value may contain only letters, numbers '
-                  'and @/./+/-/_ characters.'),
-                'invalid'),
-        ],
         error_messages={
             'unique': _("A user with that username already exists.")
         }

platform/pulpcore/app/serializers/consumer.py

@@ -1,6 +1,7 @@
 from gettext import gettext as _
 
 from rest_framework import serializers
+from rest_framework.validators import UniqueValidator
 
 from pulpcore.app import models
 from pulpcore.app.serializers import GenericKeyValueRelatedField, ModelSerializer
@@ -13,7 +14,8 @@ class ConsumerSerializer(ModelSerializer):
     )
 
     name = serializers.CharField(
-        help_text=_("The consumer common name.")
+        help_text=_("The consumer common name."),
+        validators=[UniqueValidator(queryset=models.Consumer.objects.all())]
     )
 
     description = serializers.CharField(

platform/pulpcore/app/serializers/repository.py

@@ -1,6 +1,9 @@
 from gettext import gettext as _
 
+from django.core import validators
+
 from rest_framework import serializers
+from rest_framework.validators import UniqueValidator, UniqueTogetherValidator
 from rest_framework_nested.serializers import NestedHyperlinkedModelSerializer
 
 from pulpcore.app import models
@@ -25,7 +28,8 @@ class RepositorySerializer(ModelSerializer):
         lookup_field='name',
     )
     name = serializers.CharField(
-        help_text=_('A unique name for this repository.')
+        help_text=_('A unique name for this repository.'),
+        validators=[UniqueValidator(queryset=models.Repository.objects.all())]
     )
 
     description = serializers.CharField(
@@ -148,6 +152,12 @@ class Meta:
             'ssl_client_certificate', 'ssl_client_key', 'ssl_validation', 'proxy_url',
             'username', 'password', 'last_synced', 'last_updated', 'repository',
         )
+        validators = [
+            UniqueTogetherValidator(
+                queryset=models.Importer.objects.all(),
+                fields=('name', 'repository')
+            )
+        ]
 
 
 class PublisherSerializer(MasterModelSerializer, NestedHyperlinkedModelSerializer):
@@ -168,7 +178,7 @@ class PublisherSerializer(MasterModelSerializer, NestedHyperlinkedModelSerialize
     repository = HrefWritableRepositoryRelatedField(read_only=True)
 
     auto_publish = serializers.BooleanField(
-        help_text=_('An indicaton that the automatic publish may happen when'
+        help_text=_('An indication that the automatic publish may happen when'
                     ' the repository content has changed.'),
         required=False
     )
@@ -191,6 +201,12 @@ class Meta:
         fields = MasterModelSerializer.Meta.fields + (
             'name', 'last_updated', 'repository', 'auto_publish', 'last_published', 'distributions',
         )
+        validators = [
+            UniqueTogetherValidator(
+                queryset=models.Publisher.objects.all(),
+                fields=('name', 'repository')
+            )
+        ]
 
 
 class DistributionSerializer(ModelSerializer):
@@ -202,9 +218,21 @@ class DistributionSerializer(ModelSerializer):
     )
     name = serializers.CharField(
         help_text=_('The name of the distribution. Ex, `rawhide` and `stable`.'),
+        validators=[validators.MaxLengthValidator(
+            models.Distribution._meta.get_field('name').max_length,
+            message=_('Distribution name length must be less than {} characters').format(
+                models.Distribution._meta.get_field('name').max_length
+            ))]
     )
     base_path = serializers.CharField(
         help_text=('The base (relative) path component of the published url.'),
+        validators=[validators.MaxLengthValidator(
+            models.Distribution._meta.get_field('base_path').max_length,
+            message=_('Distribution base_path length must be less than {} characters').format(
+                models.Distribution._meta.get_field('base_path').max_length
+            )),
+            UniqueValidator(queryset=models.Distribution.objects.all()),
+        ],
     )
     auto_updated = serializers.BooleanField(
         help_text=_('The publication is updated automatically when the publisher has created a '

platform/pulpcore/app/serializers/user.py

@@ -1,5 +1,6 @@
 from gettext import gettext as _
 
+from django.core import validators
 from django.conf import settings
 from django.contrib.auth.hashers import make_password
 from django.utils import six
@@ -31,8 +32,20 @@ class UserSerializer(ModelSerializer):
                                                  lookup_field='username')
 
     username = serializers.CharField(
-        help_text=_("Required. 150 characters or fewer. Letters, digits and @/./+/-/_ only."),
-        validators=[UniqueValidator(queryset=User.objects.all())],
+        help_text=_("Required. {} characters or fewer. Letters, digits and @/./+/-/_ only.").format(
+            User._meta.get_field('username').max_length),
+        validators=[UniqueValidator(queryset=User.objects.all()),
+                    validators.RegexValidator(
+                        regex=r'^[\w.@+-]+$',
+                        message=_(
+                            'Enter a valid username. This value may contain only letters, numbers'
+                            ' and @/./+/-/_ characters.'),
+                        code='invalid'),
+                    validators.MaxLengthValidator(
+                        User._meta.get_field('username').max_length,
+                        message=_('The length of username must be less than {} characters').format(
+                            User._meta.get_field('username').max_length)),
+                    ],
     )
 
     is_superuser = serializers.BooleanField(
@@ -49,11 +62,16 @@ class UserSerializer(ModelSerializer):
     jwt_secret = serializers.CharField(
         help_text=_("User JWT authentication secret"),
         required=False,
-        write_only=not settings.DEBUG  # If pulp in DEBUG mode secret is visible
+        write_only=not settings.DEBUG,  # If pulp in DEBUG mode secret is visible
+        validators=[validators.MaxLengthValidator(
+            User._meta.get_field('jwt_secret').max_length,
+            message=_('The length of jwt_secret must be less than {} characters').format(
+                User._meta.get_field('jwt_secret').max_length))
+        ],
     )
 
     reset_jwt_secret = serializers.BooleanField(
-        help_text=_("Rest user JWT secret."),
+        help_text=_("Reset user JWT secret."),
         required=False,
         write_only=True,
     )