doc: add release notes for base extended addresses and shims

Author: kwvg

doc/release-notes-6666.md

@@ -0,0 +1,65 @@
+Notable Changes
+---------------
+
+* Dash Core has added support for the ability to register multiple addr:port pairs to a masternode and for specifying
+  distinct addresses for platform P2P and platform HTTPS endpoints. The consensus and format changes needed to enable
+  this capability is referred to as "extended addresses" and is enabled by the deployment of the v23 fork, affecting
+  new masternode registrations and service updates to basic BLS masternodes.
+  * Operators must upgrade from legacy BLS scheme to basic BLS scheme before utilizing extended address capabilities
+
+Additional Notes
+----------------
+
+* While the field `service` is deprecated (see dash#6665), its effective value can be obtained by querying
+  `addresses['core_p2p'][0]`.
+
+* If the masternode is eligible for extended addresses, operators may register non-IPv4 addresses, subject to validation
+  and consensus rules.
+
+Updated RPCs
+------------
+
+* The input field `platformP2PPort` has been renamed to `platformP2PAddrs`. In addition to numeric inputs (i.e. ports),
+  the field can now accept a string (i.e. an addr:port pair) and arrays of strings (i.e. multiple addr:port pairs),
+  subject to validation rules.
+
+* The input field `platformHTTPPort` has been renamed to `platformHTTPSAddrs`. In addition to numeric inputs (i.e. ports),
+  the field can now accept a string (i.e. an addr:port pair) and arrays of strings (i.e. multiple addr:port pairs),
+  subject to validation rules.
+
+* The field `addresses` will now also report on platform P2P and platform HTTPS endpoints as `addresses['platform_p2p']`
+  and `addresses['platform_https']` respectively.
+  * On payloads before extended addresses, if a masternode update affects `platformP2PPort` and/or `platformHTTPPort`
+    but does not affect `netInfo`, `protx listdiff` does not contain enough information to report on the masternode's
+    address and will report the changed port paired with the dummy address `255.255.255.255`.
+
+    This does not affect `protx listdiff` queries where `netInfo` was updated or diffs relating to masternodes that
+    have upgraded to extended addresses.
+
+* If the masternode is eligible for extended addresses, `protx register{,_evo}` and `register_fund{,_evo}` will continue
+  allowing `coreP2PAddrs` to be left blank, as long as `platformP2PAddrs` and `platformHTTPSAddrs` are _also_ left blank.
+  * Attempting to populate any three address fields will make populating all fields mandatory.
+  * This does not affect nodes ineligible for extended addresses (i.e. all nodes before fork activation or legacy BLS nodes)
+    and they will have to continue specifying `platformP2PAddrs` and `platformHTTPSAddrs` even if they wish to keep
+    `coreP2PAddrs` blank.
+
+* If the masternode is eligible for extended addresses, `protx register{,_evo}` and `register_fund{,_evo}` will no longer
+  default to the core P2P port if a port is not specified in the addr:port pair. All ports must be specified explicitly.
+  * This does not affect nodes ineligible for extended addresses, continuing to default to the core P2P port if provided an
+    addr without a port.
+
+* `protx register{,_evo}` and `register_fund{,_evo}` will continue to allow specifying only the port number for `platformP2PAddrs`
+  and `platformHTTPSAddrs`, pairing it with the address from the first `coreP2PAddrs` entry. This mirrors existing behavior.
+  * This method of entry may not be available in future releases of Dash Core and operators are recommended to switch over to
+    explicitly specifying (arrays of) addr:port strings for all address fields.
+
+* When reporting on extended address payloads, `platformP2PPort` and `platformHTTPPort` will read the port value from
+  `netInfo[PLATFORM_P2P][0]` and `netInfo[PLATFORM_HTTPS][0]` respectively as both fields are subsumed into `netInfo`.
+  * If `netInfo` is blank (which is allowed by ProRegTx), `platformP2PPort` and `platformHTTPPort` will report `-1` to indicate
+    that the port number cannot be determined.
+  * `protx listdiff` will not report `platformP2PPort` or `platformHTTPPort` if the legacy fields were not updated (i.e.
+    changes to `netInfo` will not translate into reporting). This is because `platformP2PPort` or `platformHTTPPort` have
+    dedicated diff flags and post-consolidation, all changes are now affected by `netInfo`'s diff flag.
+
+    To avoid the perception of changes to fields that not serialized by extended address payloads, data from `netInfo` will
+    not be translated for this RPC call.