Enable Cross-Origin Resource Sharing

Issue:
https://github.com/genenetwork/gn-gemtext-threads/blob/main/topics/gn1-migration-to-gn2/clustering.gmi

* gn3/api/heatmaps.py: Fix bugs in data parsing
* gn3/app.py: enable CORS
* gn3/settings.py: add flask-cors configurations
* guix.scm: Add flask-cors dependency

  For easier testing of the heatmaps generation feature, this commit activates
  the cross-origin resource sharing for all "localhost" origins.

1 files changed, 7 insertions, 0 deletions

diff --git a/gn3/app.py b/gn3/app.py
index b4b08d0..6b4c57e 100644
--- a/gn3/app.py
+++ b/gn3/app.py
@@ -11,6 +11,7 @@ from gn3.api.heatmaps import heatmaps
 from gn3.api.correlation import correlation
 from gn3.api.data_entry import data_entry
 
+from flask_cors import CORS
 
 def create_app(config: Union[Dict, str, None] = None) -> Flask:
     """Create a new flask object"""
@@ -18,6 +19,12 @@ def create_app(config: Union[Dict, str, None] = None) -> Flask:
     # Load default configuration
     app.config.from_object("gn3.settings")
 
+    CORS(
+        app,
+        origins=app.config["CORS_ORIGINS"],
+        allow_headers=app.config["CORS_HEADERS"],
+        supports_credentials=True, intercept_exceptions=False)
+
     # Load environment configuration
     if "GN3_CONF" in os.environ:
         app.config.from_envvar('GN3_CONF')