Merge pull request #1 from kumulynja/bip77-pj-uri-encoding

BIP 77: Propose to encode `+` as `%2B` in pj param of Bitcoin URIs

Author: kumulynja

bip-0077.md

@@ -233,8 +233,10 @@ fragment of the Bitcoin URI.
 These session-specific parameters use a bech32-inspired encoding.
 The HRP is used as the parameter key, followed by the '1' separator,
 followed by the parameter value encoded using the bech32 character set in
-[uppercase](#uppercase-url). No checksum is used. Parameters are separated
-by a `+` character.
+[uppercase](#uppercase-url). No checksum is used. Parameters are separated by a + character, 
+which must be [RFC 3986
+percent-encoded](https://datatracker.ietf.org/doc/html/rfc3986#section-2.1) as `%2B` to avoid it being interpreted as a space in Bitcoin URI query parameters.
+To preserve QR alphanumeric mode compatibility, `%2B` ([uppercase](#uppercase-url)) should be used instead of `%2b`.
 
 The following parameters are defined, and must be provided in reverse
 lexicographical order:
@@ -253,7 +255,7 @@ lexicographical order:
   time](https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_16).
 
 For example, a properly encoded endpoint Bitcoin URI looks like this
-`bitcoin:tb1q6q6de88mj8qkg0q5lupmpfexwnqjsr4d2gvx2p?amount=0.00666666&pjos=0&pj=HTTPS://PAYJO.IN/TXJCGKTKXLUUZ%23RK1Q0DJS3VVDXWQQTLQ8022QGXSX7ML9PHZ6EDSF6AKEWQG758JPS2EV+OH1QYPM59NK2LXXS4890SUAXXYT25Z2VAPHP0X7YEYCJXGWAG6UG9ZU6NQ+EX1WKV8CEC`
+`bitcoin:tb1q6q6de88mj8qkg0q5lupmpfexwnqjsr4d2gvx2p?amount=0.00666666&pjos=0&pj=HTTPS://PAYJO.IN/TXJCGKTKXLUUZ%23RK1Q0DJS3VVDXWQQTLQ8022QGXSX7ML9PHZ6EDSF6AKEWQG758JPS2EV%2BOH1QYPM59NK2LXXS4890SUAXXYT25Z2VAPHP0X7YEYCJXGWAG6UG9ZU6NQ%2BEX1WKV8CEC`
 
 ### Sender Original PSBT Messaging