Add user-defined category-label colors (#1402)

* Add user-defined category-label colors

Fixes https://github.com/chanzuckerberg/cellxgene/issues/1152

As described in https://github.com/chanzuckerberg/cellxgene/issues/1307

* Respond to feedback from @bkmartinjr in nodejs

* Respond to feedback from @bkmartinjr in python

* Add tests to the server module

* Autoformat python, run linter

* Make colors_get error handling specific

* Respond to feedback from @bkmartinjr

* Respond to feedback from @bkmartinjr

* Fix whitespace

* Fix python lint errrors

* Update documentation

* Add --disable-user-colors option to launch and cxgtool.py

* Fix python formatting

* Rename '--disable-user-colors' to '--disable-custom-colors'

server/common/rest.py

@@ -1,9 +1,11 @@
-import sys
-from http import HTTPStatus
 import copy
 import logging
+import sys
+from http import HTTPStatus
+
 from flask import make_response, jsonify, current_app, abort
 from werkzeug.urls import url_unquote
+
 from server.common.constants import Axis, DiffExpMode, JSON_NaN_to_num_warning_msg
 from server.common.errors import (
     FilterError,
@@ -12,6 +14,7 @@ from server.common.errors import (
     DisabledFeatureError,
     ExceedsLimitError,
     DatasetAccessError,
+    ColorFormatException,
 )
 
 import json
@@ -222,6 +225,15 @@ def data_var_get(request, data_adaptor):
         return abort_and_log(HTTPStatus.BAD_REQUEST, str(e), include_exc_info=True)
 
 
+def colors_get(data_adaptor):
+    if not data_adaptor.config.presentation__custom_colors:
+        return make_response(jsonify({}), HTTPStatus.OK)
+    try:
+        return make_response(jsonify(data_adaptor.get_colors()), HTTPStatus.OK)
+    except ColorFormatException as e:
+        return abort_and_log(HTTPStatus.NOT_FOUND, str(e), include_exc_info=True)
+
+
 def diffexp_obs_post(request, data_adaptor):
     if not data_adaptor.config.diffexp__enable:
         return abort(HTTPStatus.NOT_IMPLEMENTED)