chore: rename metafield key to function-configuratoin

Author: mathiusj

discounts/javascript/discounts-allocator/default/src/run.graphql.liquid

@@ -1,6 +1,6 @@
 query RunInput {
   shop {
-    metafield(namespace: "$app:{{handle | replace: " ", "-" | downcase}}", key: "allocator-function") {
+    metafield(namespace: "$app:{{handle | replace: " ", "-" | downcase}}", key: "function-configuration") {
       value
     }
   }

discounts/rust/discounts-allocator/default/shopify.extension.toml.liquid

@@ -1,7 +1,7 @@
 api_version = "unstable"
 
 [[extensions]]
-handle = "discounts-allocator"
+handle = "{{handle}}"
 name = "t:name"
 description = "t:description"
 type = "function"

discounts/rust/discounts-allocator/default/src/run.graphql.liquid

@@ -1,6 +1,6 @@
 query Input {
   shop {
-    metafield(namespace: "$app:{{handle | replace: " ", "-" | downcase}}", key: "allocator-function") {
+    metafield(namespace: "$app:{{handle | replace: " ", "-" | downcase}}", key: "function-configuration") {
       value
     }
   }