Add basic authentication in the server (#1670)

* Add basic authentication in the server

A pattern for creating authentication methods is introduced, with three
authentication types defined:
  none - no authentication
  session - like the current session based auth used for user annotations
  test - used to test the login/logout process end to end

The config endpoint now returns informations about the authentication, like if
the user is authenticated and their username.  The redirect uri's for login and
logout are also returned if the authentication type requires login

This is the first a several PRs for authentication.

*. Update server tests to avoid hardcoded ports

test_api and test_nan_rest now use a common function for starting a test server,
than will initially choose a random port.

server/common/annotations.py

@@ -1,6 +1,5 @@
 from datetime import datetime
 import re
-from uuid import uuid4
 import os
 import pandas as pd
 from hashlib import blake2b
@@ -11,7 +10,7 @@ from server.common.errors import AnnotationsError, OntologyLoadFailure
 from server.common.utils import series_to_schema
 import fsspec
 import fastobo
-from flask import session
+from flask import session, current_app
 from abc import ABCMeta, abstractmethod
 
 
@@ -80,7 +79,6 @@ class Annotations(metaclass=ABCMeta):
 
 class AnnotationsLocalFile(Annotations):
 
-    CXGUID = "cxguid"
     CXG_ANNO_COLLECTION = "cxg_anno_collection"
 
     def __init__(self, output_dir, output_file):
@@ -159,18 +157,12 @@ class AnnotationsLocalFile(Annotations):
             self.last_fname = fname
             self.last_labels = df
 
-    def _get_userid(self):
-        if self.CXGUID not in session:
-            session[self.CXGUID] = uuid4().hex
-            session.permanent = True
-        return session[self.CXGUID]
-
     def _get_userdata_idhash(self, data_adaptor):
         """
         Return a short hash that weakly identifies the user and dataset.
         Used to create safe annotations output file names.
         """
-        uid = self._get_userid()
+        uid = current_app.auth.get_userid()
         id = (uid + data_adaptor.get_location()).encode()
         idhash = base64.b32encode(blake2b(id, digest_size=5).digest()).decode("utf-8")
         return idhash
@@ -257,8 +249,9 @@ class AnnotationsLocalFile(Annotations):
 
         elif session is not None:
             collection = self.get_collection()
-            params["annotations-user-data-idhash"] = self._get_userdata_idhash(data_adaptor)
-            params["annotations-data-collection-is-read-only"] = False
-            params["annotations-data-collection-name"] = collection
+            if current_app.auth.is_authenticated():
+                params["annotations-user-data-idhash"] = self._get_userdata_idhash(data_adaptor)
+                params["annotations-data-collection-is-read-only"] = False
+                params["annotations-data-collection-name"] = collection
 
         parameters.update(params)