Add support for custom registration fields for registry

docs/parameters.yaml

@@ -624,7 +624,7 @@ description: >-
   ```
 
   Note the following requirements:
-  - "name" must be snake case with underline connecting words, i.e. site_name. 
+  - "name" must be snake case with underline connecting words, i.e. site_name.
   - "type" must be one of "string", "int", "bool", "datetime" (Unix time in seconds), or "enum".
   - "options" must be a non-empty yaml array for field with type "enum". "optionsUrl" will be ignored if "options" is set.
     example:
@@ -645,7 +645,7 @@ description: >-
         }
       ]
       ```
-  - "validationUrl" is an optional, user-provided validation endpoint 
+  - "validationUrl" is an optional, user-provided validation endpoint
       that listens to a POST request with JSON body of {"field": "<field value>"}
       and responds with a 200 code and JSON of {"valid": bool, "message": ""}. If it's non-empty,
       for all create and update of namespace registration, this URL will be called
@@ -655,6 +655,43 @@ type: object
 default: none
 components: ["nsregistry"]
 ---
+name: Registry.InstitutionsUrl
+description: >-
+  A url to get a list of available institutions for users to register their namespaces to.
+  The url must accept a GET request with 200 response in JSON/YAML content with the following format:
+
+  JSON:
+  ```JSON
+    [
+      {
+        "name": "University of Wisconsin - Madison",
+        "id": " https://osg-htc.org/iid/01y2jtd41"
+      }
+    ]
+  ```
+
+  YAML:
+  ```yaml
+    ---
+    - name: University of Wisconsin - Madison
+      id: " https://osg-htc.org/iid/01y2jtd41"
+  ```
+
+  where the id field will be stored in registry database and must be unique, and name field will be displayed in UI as the option.
+
+  Note that Pelican will cache the response of the url in a TTL cache with default refresh time of 15 minutes.
+  Also note that Registry.Institutions will take precedence over this value if both are set.
+type: url
+default: none
+components: ["nsregistry"]
+---
+name: Registry.InstitutionsUrlReloadMinutes
+description: >-
+  Number of minutes that the Registry.InstitutionsUrl will be reloaded into the TTL cache.
+type: duration
+default: 15m
+components: ["nsregistry"]
+---
 ############################
 #   Server-level configs   #
 ############################

registry/registry_ui.go

@@ -92,6 +92,8 @@ const (
 var (
 	registrationFields     []registrationField
 	customRegFieldsConfigs []customRegFieldsConfig
+	institutionsCache      *ttlcache.Cache[string, []Institution]
+	institutionsCacheMutex = sync.RWMutex{}
 )
 
 func init() {