Add interface for PeerData (not a libp2p req)

peer/peerdata_interface.py

@@ -0,0 +1,51 @@
+from abc import ABC, abstractmethod
+
+class IPeerData(ABC):
+
+	def __init__(self, context):
+        self.context = context
+
+    """
+	:return: all protocols associated with given peer
+	"""
+    def get_protocols(self):
+    	pass
+
+    """
+    :param protocols: protocols to add
+	"""
+    def add_protocols(self, protocols):
+    	pass
+
+    """
+    :param addrs: multiaddresses to add
+	"""
+    def add_addrs(self, addrs):
+    	pass
+
+    """
+    :return: all multiaddresses
+	"""
+    def get_addrs(self):
+    	pass
+
+    """
+    Clear all addresses
+    """
+    def clear_addrs(self):
+    	pass
+
+    """
+    :param key: key in KV pair
+    :param val: val to associate with key
+    """
+    def put_metadata(self, key, val):
+    	pass
+
+    """
+    :param key: key in KV pair
+    :return: val for key, error (only defined if key not found)
+    """
+    def get_metadata(self, key):
+    	pass
+