Update MessageInfo docs, which is not used in migrate anymore

packages/std/schema/message_info.json

@@ -1,15 +1,15 @@
 {
   "$schema": "http://json-schema.org/draft-07/schema#",
   "title": "MessageInfo",
-  "description": "MessageInfo is sent with `init`, `handle`, and `migrate` calls, but not with queries. It contains the essential info for authorization - identity of the call, and payment",
+  "description": "Additional information from [MsgInstantiateContract] and [MsgExecuteContract], which is passed along with the contract execution message into the `init` and `handle` entry points.\n\nIt contains the essential info for authorization - identity of the call, and payment.\n\n[MsgInstantiateContract]: https://github.com/CosmWasm/wasmd/blob/v0.15.0/x/wasm/internal/types/tx.proto#L47-L61 [MsgExecuteContract]: https://github.com/CosmWasm/wasmd/blob/v0.15.0/x/wasm/internal/types/tx.proto#L68-L78",
   "type": "object",
   "required": [
     "sender",
     "sent_funds"
   ],
   "properties": {
     "sender": {
-      "description": "The `sender` field from the `wasm/MsgStoreCode`, `wasm/MsgInstantiateContract`, `wasm/MsgMigrateContract` or `wasm/MsgExecuteContract` message. You can think of this as the address that initiated the action (i.e. the message). What that means exactly heavily depends on the application.\n\nThe x/wasm module ensures that the sender address signed the transaction. Additional signers of the transaction that are either needed for other messages or contain unnecessary signatures are not propagated into the contract.\n\nThere is a discussion to open up this field to multiple initiators, which you're welcome to join if you have a specific need for that feature: https://github.com/CosmWasm/cosmwasm/issues/293",
+      "description": "The `sender` field from `MsgInstantiateContract` and `MsgExecuteContract`. You can think of this as the address that initiated the action (i.e. the message). What that means exactly heavily depends on the application.\n\nThe x/wasm module ensures that the sender address signed the transaction or is otherwise authorized to send the message.\n\nAdditional signers of the transaction that are either needed for other messages or contain unnecessary signatures are not propagated into the contract.",
       "allOf": [
         {
           "$ref": "#/definitions/HumanAddr"

packages/std/src/types.rs

@@ -64,21 +64,24 @@ pub struct BlockInfo {
     pub chain_id: String,
 }
 
-/// MessageInfo is sent with `init`, `handle`, and `migrate` calls, but not with queries.
-/// It contains the essential info for authorization - identity of the call, and payment
+/// Additional information from [MsgInstantiateContract] and [MsgExecuteContract], which is passed
+/// along with the contract execution message into the `init` and `handle` entry points.
+///
+/// It contains the essential info for authorization - identity of the call, and payment.
+///
+/// [MsgInstantiateContract]: https://github.com/CosmWasm/wasmd/blob/v0.15.0/x/wasm/internal/types/tx.proto#L47-L61
+/// [MsgExecuteContract]: https://github.com/CosmWasm/wasmd/blob/v0.15.0/x/wasm/internal/types/tx.proto#L68-L78
 #[derive(Serialize, Deserialize, Clone, Default, Debug, PartialEq, JsonSchema)]
 pub struct MessageInfo {
-    /// The `sender` field from the `wasm/MsgStoreCode`, `wasm/MsgInstantiateContract`, `wasm/MsgMigrateContract`
-    /// or `wasm/MsgExecuteContract` message.
+    /// The `sender` field from `MsgInstantiateContract` and `MsgExecuteContract`.
     /// You can think of this as the address that initiated the action (i.e. the message). What that
     /// means exactly heavily depends on the application.
     ///
-    /// The x/wasm module ensures that the sender address signed the transaction.
+    /// The x/wasm module ensures that the sender address signed the transaction or
+    /// is otherwise authorized to send the message.
+    ///
     /// Additional signers of the transaction that are either needed for other messages or contain unnecessary
     /// signatures are not propagated into the contract.
-    ///
-    /// There is a discussion to open up this field to multiple initiators, which you're welcome to join
-    /// if you have a specific need for that feature: https://github.com/CosmWasm/cosmwasm/issues/293
     pub sender: HumanAddr,
     pub sent_funds: Vec<Coin>,
 }