feat: add support for parsing comma-separated list environment variab…

…les (#2765)

We're planning to add a new environment variable, `ACTOR_BUILD_TAGS`, to
the Actor runtime, which will contain the list of build tags of the
currently running Actor build. The environment variable will be a
comma-separated list, but I think it would be easier to work with if it
was already parsed to an array in the `Configuration` instance.

This adds support for parsing comma-separated list environment variables
to arrays. In the SDK, I'll then just override the
`COMMA_SEPARATED_LIST_VARS` list to include the environment variable I
want to have parsed.

packages/core/src/configuration.ts

@@ -253,6 +253,8 @@ export class Configuration {
 
     protected static INTEGER_VARS = ['memoryMbytes', 'persistStateIntervalMillis', 'systemInfoIntervalMillis'];
 
+    protected static COMMA_SEPARATED_LIST_VARS: string[] = [];
+
     protected static DEFAULTS: Dictionary = {
         defaultKeyValueStoreId: 'default',
         defaultDatasetId: 'default',
@@ -344,6 +346,13 @@ export class Configuration {
             return !['0', 'false', ''].includes(String(value).toLowerCase());
         }
 
+        if (Configuration.COMMA_SEPARATED_LIST_VARS.includes(key)) {
+            if (!value) return [];
+            return String(value)
+                .split(',')
+                .map((v) => v.trim());
+        }
+
         return value;
     }