docs: Update MIGRATING.md

MIGRATING.md

@@ -2,6 +2,63 @@
 
 This guide explains what is needed to upgrade contracts when migrating over major releases of `sylvia`. Note that you can also view the [complete CHANGELOG](https://github.com/CosmWasm/sylvia/blob/main/CHANGELOG.md) to understand the differences.
 
+
+## 1.0.2 -> 
+
+### Remove types forwarding to interface in `sv::messages`
+
+1. Types forwarding to the messages' associated types is not required:
+```rust
+// In sylvia 1.0.2
+#[contract]
+#[sv::messages(generic<SomeType1, SomeType2, SomeType3> as Generic: custom(msg, query))]
+impl Contract {}
+
+// Current Sylvia version:
+#[contract]
+#[sv::messages(generic as Generic: custom(msg, query))]
+impl Contract {}
+```
+
+This change is optional, since the generics are still accepted by the parser. Though they are
+ignored in the further process.
+
+
+2. Multitest's `CodeId` is now generic over the contract type, not only the generics of the contract:
+```rust
+// In sylvia 1.0.2
+let code_id: CodeId<
+    SvCustomMsg,
+    SvCustomMsg,
+    _,
+> = CodeId::store_code(&app);
+
+// Current Sylvia version:
+let code_id: CodeId<
+    GenericContract<
+        SvCustomMsg,
+        SvCustomMsg,
+    >,
+    _,
+> = CodeId::store_code(&app);
+```
+
+3. Lifetime ellision in a contract's implementation block is not supported anymore.
+```rust
+// In sylvia 1.0.2
+#[contract]
+impl Cw1SubkeysContract<'_> {
+    // [...]
+}
+
+// Current Sylvia version:
+#[contract]
+impl<'a> Cw1SubkeysContract<'a> {
+    // [...]
+}
+```
+
+
 ## 0.9.3 -> 0.10.0
 
 ## Multitest proxy