feat: add delta api streaming flag (#9269)

Lets add separate flag for delta streaming.

Author: sjaanus

src/lib/types/experimental.ts

@@ -61,6 +61,7 @@ export type IFlagKey =
     | 'streaming'
     | 'etagVariant'
     | 'deltaApi'
+    | 'deltaApiStreaming'
     | 'uniqueSdkTracking'
     | 'frontendHeaderRedesign'
     | 'dataUsageMultiMonthView'
@@ -293,6 +294,10 @@ const flags: IFlags = {
         process.env.UNLEASH_EXPERIMENTAL_DELTA_API,
         false,
     ),
+    deltaApiStreaming: parseEnvVarBoolean(
+        process.env.UNLEASH_EXPERIMENTAL_DELTA_API_STREAMING,
+        false,
+    ),
     uniqueSdkTracking: parseEnvVarBoolean(
         process.env.UNLEASH_EXPERIMENTAL_UNIQUE_SDK_TRACKING,
         false,