chore: null -> optional

04.md

@@ -26,7 +26,7 @@ The wallet of `Alice` includes the following `PostMintQuoteBolt11Request` data i
 {
   "amount": <int>,
   "unit": <str_enum["sat"]>,
-  "description": <str|null>
+  "description": <str> // Optional
 }
 ```
 

20.md

@@ -8,8 +8,7 @@
 
 This NUT defines signature-based authentication for mint quote redemption. When requesting a mint quote, clients provide a public key. The mint will then require a valid signature from the corresponding secret key to process the mint operation.
 
-> [!CAUTION]
-> [NUT-04][04] mint quotes without a public key can be minted by anyone who knows the mint quote id without providing a signature.
+> [!CAUTION] > [NUT-04][04] mint quotes without a public key can be minted by anyone who knows the mint quote id without providing a signature.
 
 ## Mint quote
 
@@ -25,17 +24,16 @@ The wallet of `Alice` includes the following `PostMintQuoteBolt11Request` data i
 {
   "amount": <int>,
   "unit": <str_enum["sat"]>,
-  "description": <str|null>,
-  "pubkey": <str|null> <-- New
+  "description": <str>, // Optional
+  "pubkey": <str> // Optional <-- New
 }
 ```
 
 with the requested `amount`,`unit`, and `description` according to [NUT-04][04].
 
 `pubkey` is the public key that will be required for signature verification during the minting operation. The mint will only mint ecash after receiving a valid signature from the corresponding private key in the subsequent `PostMintRequest`.
 
-> [!IMPORTANT]
-> **Privacy:** To prevent the mint from being able to link multiple mint quotes, wallets **SHOULD** generate a unique public key for each mint quote request.
+> [!IMPORTANT] > **Privacy:** To prevent the mint from being able to link multiple mint quotes, wallets **SHOULD** generate a unique public key for each mint quote request.
 
 The mint `Bob` then responds with a `PostMintQuoteBolt11Response`:
 
@@ -45,7 +43,7 @@ The mint `Bob` then responds with a `PostMintQuoteBolt11Response`:
   "request": <str>,
   "state": <str_enum[STATE]>,
   "expiry": <int>,
-  "pubkey": <str|null> <-- New
+  "pubkey": <str> // Optional <-- New
 }
 ```