Add module Stream private mention

DOCUMENTATION.md

@@ -342,6 +342,44 @@ Some notes about the intents being satisfied here:
   sibling code in adjacent `module`s should not be using them directly (in
   general interaction should be via the `type Service`)
 
+✅ DO keep `module Stream` visibility `private`, present via `module Reactions`
+
+If the composition of stream names is relevant for Reactions processing, expose relevant helpers in a `module Reactions` facade.
+For instance, rather than having external reaction logic refer to `Aggregate.Stream.Category`, expose a facade such as:
+
+```fsharp
+module Reactions =
+
+    let streamName = Stream.name
+    let deletionNamePrefix tenantIdStr = $"%s{Stream.Category}-%s{tenantIdStr}"
+```
+
+✅ DO use tupled arguments for the `Stream.id` function
+
+All the inputs of which the `StreamId` is composed should be represented as one argument:
+
+```fsharp
+✅ let id struct (tenantId, clientId) = FsCodec.StreamId.gen2 TenantId.toString ClientId.toString (tenantId, clientId)
+✅ let id = FsCodec.StreamId.gen2 TenantId.toString ClientId.toString
+❌ let id tenantId clientId = FsCodec.StreamId.gen2 TenantId.toString ClientId.toString (tenantId, clientId)
+```
+
+✅ DO keep `module Stream` visibility `private`, present via `module Reactions`
+
+If the composition of stream names is relevant for Reactions processing, expose relevant helpers in a `module Reactions` facade.
+For instance, rather than having external reaction logic refer to `Aggregate.Stream.Category`, expose a facade such as:
+
+```fsharp
+module Reactions =
+
+    let streamName = Stream.name
+    let deletionNamePrefix tenantIdStr = $"%s{Stream.Category}-%s{tenantIdStr}"
+    let [<return: Struct>] (|For|_|) = Stream.tryDecode
+    let [<return: Struct>] (|Decode|_|) = function
+        | struct (For id, _) & Streams.Decode dec events -> ValueSome struct (id, events)
+        | _ -> ValueNone
+```
+
 ```fsharp
 module Fold =