feat: add max expiry signaling

19.md

@@ -26,7 +26,7 @@ The wallet of `Alice` includes the following `PostMintQuoteBolt12Request` data i
 }
 ```
 
-The `amount` field is optional and specifies the amount to mint. The `unit` field is mandatory. An optional `description` can be passed if the mint signals support for it in `MintMethodSetting`. If `single_use` is false, the offer can be paid multiple times. The optional `expiry` field specifies the unix timestamp when the offer expires.
+The `amount` field is optional and specifies the amount to mint. The `unit` field is mandatory. An optional `description` can be passed if the mint signals support for it in `MintMethodSetting`. If `single_use` is false, the offer can be paid multiple times. The optional `expiry` field specifies the unix timestamp when the offer expires it **MUST** be before the `max_expiry` in the `MintMethodSettings` if one is given.
 
 The mint `Bob` then responds with a `PostMintQuoteBolt12Response`:
 
@@ -141,11 +141,13 @@ The settings for this nut indicate the supported method-unit pairs for minting a
   "unit": <str>,
   "min_amount": <int|null>,
   "max_amount": <int|null>,
-  "description": <bool|null>
+  "description": <bool|null>,
+  "max_expiry": <int|null>
 }
 ```
 
-`min_amount` and `max_amount` indicate the minimum and maximum amount for an operation of this method-unit pair.
+`min_amount` and `max_amount` define the allowed range for transactions using this method-unit pair. `max_expiry` specifies the latest timestamp (in Unix time) until which payments for this offer will be accepted.
+
 
 Example `MintMethodSetting`:
 
@@ -155,7 +157,8 @@ Example `MintMethodSetting`:
   "unit": "sat",
   "min_amount": 0,
   "max_amount": 10000,
-  "description": true
+  "description": true,
+  "max_expiry": 1825076378
 }
 ```