add support for AWS Organizations

endpoints covers so far:
- create_organization
- describe_organization
- create_account
- describe_account
- list_accounts

all tests passing.
could use some advise from maintaners.

moto/organizations/models.py

@@ -0,0 +1,131 @@
+from __future__ import unicode_literals
+
+import datetime
+import time
+
+from moto.core import BaseBackend, BaseModel
+from moto.core.utils import unix_time
+from moto.organizations import utils
+
+MASTER_ACCOUNT_ID = '123456789012'
+MASTER_ACCOUNT_EMAIL = 'fakeorg@moto-example.com'
+ORGANIZATION_ARN_FORMAT = 'arn:aws:organizations::{0}:organization/{1}'
+MASTER_ACCOUNT_ARN_FORMAT = 'arn:aws:organizations::{0}:account/{1}/{0}'
+ACCOUNT_ARN_FORMAT = 'arn:aws:organizations::{0}:account/{1}/{2}'
+
+
+class FakeOrganization(BaseModel):
+
+    def __init__(self, feature_set):
+        self.id = utils.make_random_org_id()
+        self.feature_set = feature_set
+        self.master_account_id = MASTER_ACCOUNT_ID
+        self.master_account_email = MASTER_ACCOUNT_EMAIL
+        self.available_policy_types = [{
+            'Type': 'SERVICE_CONTROL_POLICY',
+            'Status': 'ENABLED'
+        }]
+    
+    @property
+    def arn(self):
+        return ORGANIZATION_ARN_FORMAT.format(self.master_account_id, self.id)
+
+    @property
+    def master_account_arn(self):
+        return MASTER_ACCOUNT_ARN_FORMAT.format(self.master_account_id, self.id)
+
+    def _describe(self):
+        return {
+            'Organization': {
+                'Id': self.id,
+                'Arn': self.arn,
+                'FeatureSet': self.feature_set,
+                'MasterAccountArn': self.master_account_arn,
+                'MasterAccountId': self.master_account_id,
+                'MasterAccountEmail': self.master_account_email,
+                'AvailablePolicyTypes': self.available_policy_types,
+            }
+        }
+
+
+class FakeAccount(BaseModel):
+
+    def __init__(self, organization, **kwargs):
+        self.organization_id = organization.id
+        self.master_account_id = organization.master_account_id
+        self.create_account_status_id = utils.make_random_create_account_status_id()
+        self.account_id = utils.make_random_account_id()
+        self.account_name = kwargs['AccountName']
+        self.email = kwargs['Email']
+        self.create_time = datetime.datetime.utcnow()
+        self.status = 'ACTIVE'
+        self.joined_method = 'CREATED'
+
+    @property
+    def arn(self):
+        return ACCOUNT_ARN_FORMAT.format(
+            self.master_account_id,
+            self.organization_id,
+            self.account_id
+        )
+
+    @property
+    def create_account_status(self):
+        return {
+            'CreateAccountStatus': {
+                'Id': self.create_account_status_id,
+                'AccountName': self.account_name,
+                'State': 'SUCCEEDED',
+                'RequestedTimestamp': unix_time(self.create_time),
+                'CompletedTimestamp': unix_time(self.create_time),
+                'AccountId': self.account_id,
+            }
+        }
+
+    def describe(self):
+        return {
+            'Account': {
+                'Id': self.account_id,
+                'Arn': self.arn,
+                'Email': self.email,
+                'Name': self.account_name,
+                'Status': self.status,
+                'JoinedMethod': self.joined_method,
+                'JoinedTimestamp': unix_time(self.create_time),
+            }
+        }
+
+
+class OrganizationsBackend(BaseBackend):
+
+    def __init__(self):
+        self.org = None
+        self.accounts = []
+
+    def create_organization(self, **kwargs):
+        self.org = FakeOrganization(kwargs['FeatureSet'])
+        return self.org._describe()
+
+    def describe_organization(self):
+        return self.org._describe()
+
+    def create_account(self, **kwargs):
+        new_account = FakeAccount(self.org, **kwargs)
+        self.accounts.append(new_account)
+        return new_account.create_account_status
+
+    def describe_account(self, **kwargs):
+        account = [account for account in self.accounts 
+                   if account.account_id == kwargs['AccountId']][0]
+        return account.describe()
+
+    def list_accounts(self):
+        return dict(
+            Accounts=[account.describe()['Account'] for account in self.accounts]
+        )
+
+
+organizations_backend = OrganizationsBackend()
+
+
+