Separate fragment params with - instead of +

Since only Bull Bitcoin Mobile and Cake wallet are currently deployed in
production, both using PDK, and the `+` character is causing some
friction, this change seems justified to avoid similar issues with
future implementations.

Author: nothingmuch

bip-0077.md

@@ -234,7 +234,7 @@ 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.
+by a `-` character (previously a `+` separator [was specified](#bip-77)).
 
 The following parameters are defined, and must be provided in reverse
 lexicographical order:
@@ -253,7 +253,7 @@ 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-OH1QYPM59NK2LXXS4890SUAXXYT25Z2VAPHP0X7YEYCJXGWAG6UG9ZU6NQ-EX1WKV8CEC`
 
 ### Sender Original PSBT Messaging
 
@@ -711,6 +711,8 @@ receiver also specifies the directory.
 
 ## Backwards compatibility
 
+### BIP 78
+
 Senders not supporting Payjoin will just ignore the `pj` parameter and
 proceed to typical address-based transaction flows.
 
@@ -726,6 +728,18 @@ seconds or else the directory should respond with an `unavailable` JSON
 error code as [defined in BIP
 78](https://github.com/bitcoin/bips/blob/master/bip-0078.mediawiki#receivers-well-known-errors).
 
+### BIP 77
+
+A previous version of this document specified `+` as the fragment parameter
+separator. This can cause issues due to a common convention (not specified in
+RFC 3986, but in RFC 1866 in relation to HTML form submission and query
+parameters, not URI fragments) of representing ` ` with `+` in URI query
+parameters.
+
+As a result of this change implementations are encouraged to still accept `+`
+delimited fragment parameters for during 2026 (a grace period of just under 6
+months).
+
 ## Reference implementation
 
 A production reference implementation client can be found at