Separate userinfo from the config endpoint (#1728)

* Separate userinfo from the config endpoint

previously information about if the user was logged in and their username
was part of the config endpoint.
However, the config endpoint was previously static, and has a cache control.
Rather than not caching the config, a new endpoint called "userinfo"
is created to handle that information.

The config endpoint still has the non-changing part of the authentication:

  config:
    authentication:
        requires_client_login:  True/False
        login: <uri to login endoint if requires_client_login is True>
        logout: <uri to logout endoint if requires_client_login is True>

The userinfo endpoint returns this information:

  userinfo:
    is_authenticated:  True/False
    username: <string if is_authenticated>

if authentication is not enabled then the config does not have an authentication key,
and userinfo returns None.

Also in the PR are a few minor code improvements and bug fixes

Co-authored-by: Colin Megill <colinmegill@gmail.com>

server/app/app.py

@@ -240,6 +240,13 @@ class ConfigAPI(DatasetResource):
         return common_rest.config_get(current_app.app_config, data_adaptor)
 
 
+class UserInfoAPI(DatasetResource):
+    @cache_control_always(no_store=True)
+    @rest_get_data_adaptor
+    def get(self, data_adaptor):
+        return common_rest.userinfo_get(current_app.app_config, data_adaptor)
+
+
 class AnnotationsObsAPI(DatasetResource):
     @cache_control(public=True, max_age=ONE_WEEK)
     @rest_get_data_adaptor
@@ -308,6 +315,7 @@ def get_api_resources(bp_api, url_dataroot=None):
     # Initialization routes
     add_resource(SchemaAPI, "/schema")
     add_resource(ConfigAPI, "/config")
+    add_resource(UserInfoAPI, "/userinfo")
     # Data routes
     add_resource(AnnotationsObsAPI, "/annotations/obs")
     add_resource(AnnotationsVarAPI, "/annotations/var")