Added documentation for objects/domain.py. (#264)

## 📝 Description

Added documentation for `objects/domain.py`.

## ✔️ How to Test

`pytest test`

Ticket: TPT-1924

Author: ezilber-akamai-zz

linode_api4/objects/domain.py

@@ -3,6 +3,12 @@
 
 
 class DomainRecord(DerivedBase):
+    """
+    A single record on a Domain.
+
+    API Documentation: https://www.linode.com/docs/api/domains/#domain-record-view
+    """
+
     api_endpoint = "/domains/{domain_id}/records/{id}"
     derived_url_path = "records"
     parent_id_name = "domain_id"
@@ -26,6 +32,14 @@ class DomainRecord(DerivedBase):
 
 
 class Domain(Base):
+    """
+    A single Domain that you have registered in Linode’s DNS Manager.
+    Linode is not a registrar, and in order for this Domain record to work
+    you must own the domain and point your registrar at Linode’s nameservers.
+
+    API Documentation: https://www.linode.com/docs/api/domains/#domain-view
+    """
+
     api_endpoint = "/domains/{id}"
     properties = {
         "id": Property(identifier=True),
@@ -46,6 +60,25 @@ class Domain(Base):
     }
 
     def record_create(self, record_type, **kwargs):
+        """
+        Adds a new Domain Record to the zonefile this Domain represents.
+        Each domain can have up to 12,000 active records.
+
+        API Documentation: https://www.linode.com/docs/api/domains/#domain-record-create
+
+        :param record_type: The type of Record this is in the DNS system. Can be one of:
+                            A, AAAA, NS, MX, CNAME, TXT, SRV, PTR, CAA.
+        :type: record_type: str
+
+        :param kwargs: Additional optional parameters for creating a domain record. Valid parameters
+                       are: name, target, priority, weight, port, service, protocol, ttl_sec. Descriptions
+                       of these parameters can be found in the API Documentation above.
+        :type: record_type: dict
+
+        :returns: The newly created Domain Record
+        :rtype: DomainRecord
+        """
+
         params = {
             "type": record_type,
         }
@@ -65,20 +98,58 @@ def record_create(self, record_type, **kwargs):
         return zr
 
     def zone_file_view(self):
+        """
+        Returns the zone file for the last rendered zone for the specified domain.
+
+        API Documentation: https://www.linode.com/docs/api/domains/#domain-zone-file-view
+
+        :returns: The zone file for the last rendered zone for the specified domain in the form
+                  of a list of the lines of the zone file.
+        :rtype: List[str]
+        """
+
         result = self._client.get(
             "{}/zone-file".format(self.api_endpoint), model=self
         )
 
         return result["zone_file"]
 
     def clone(self, domain: str):
+        """
+        Clones a Domain and all associated DNS records from a Domain that is registered in Linode’s DNS manager.
+
+        API Documentation: https://www.linode.com/docs/api/domains/#domain-clone
+
+        :param domain: The new domain for the clone. Domain labels cannot be longer
+                       than 63 characters and must conform to RFC1035. Domains must be
+                       unique on Linode’s platform, including across different Linode
+                       accounts; there cannot be two Domains representing the same domain.
+        :type: domain: str
+        """
         params = {"domain": domain}
 
         self._client.post(
             "{}/clone".format(self.api_endpoint), model=self, data=params
         )
 
     def domain_import(self, domain, remote_nameserver):
+        """
+        Imports a domain zone from a remote nameserver. Your nameserver must
+        allow zone transfers (AXFR) from the following IPs:
+            - 96.126.114.97
+            - 96.126.114.98
+            - 2600:3c00::5e
+            = 2600:3c00::5f
+
+        API Documentation: https://www.linode.com/docs/api/domains/#domain-import
+
+        :param domain: The domain to import.
+        :type: domain: str
+
+        :param remote_nameserver: The remote nameserver that allows zone transfers (AXFR).
+        :type: remote_nameserver: str
+        """
+
         params = {
             "domain": domain.domain if isinstance(domain, Domain) else domain,
             "remote_nameserver": remote_nameserver,