doc: changelog: fast_pair: add items related to the FMDN API changes

Updated the release changelog to describe the changes to the FMDN API
elements that are used to track the Find My Device Network (FMDN)
provisioning state.

Described the addition of the new FMDN API:
bt_fast_pair_fmdn_is_provisioned. The API can be used to check the
device provisioning state synchronously.

Described the change in the behavior of the
bt_fast_pair_fmdn_info_cb.provisioning_state_changed callback.
The callback no longer reports the initial provisioning state after
the Fast Pair subsystem is enabled with the bt_fast_pair_enable API.

Ref: NCSDK-30856

Signed-off-by: Kamil Piszczek <[email protected]>

Author: kapi-no

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -754,6 +754,9 @@ Bluetooth libraries and services
       For further details on the Android intent feature for firmware updates, see the :ref:`ug_bt_fast_pair_provisioning_register_firmware_update_intent` section in the Fast Pair integration guide.
     * A workaround for the issue where the FMDN clock value might not be correctly set after the system reboot for nRF54L Series devices.
       For details, see the ``NCSDK-32268`` issue in the :ref:`known_issues` page.
+    * A new function :c:func:`bt_fast_pair_fmdn_is_provisioned` for the FMDN extension API.
+      This function can be used to synchronously check the current FMDN provisioning state.
+      For more details, see the :ref:`ug_bt_fast_pair_gatt_service_fmdn_info_callbacks_provisioning_state` section in the Fast Pair integration guide.
 
   * Updated:
 
@@ -762,6 +765,9 @@ Bluetooth libraries and services
     * The method of supplying the Fast Pair Model ID and Anti-Spoofing Private Key to generate the Fast Pair provisioning data HEX file.
       The ``FP_MODEL_ID`` and ``FP_ANTI_SPOOFING_KEY`` CMake variables are replaced by the corresponding ``SB_CONFIG_BT_FAST_PAIR_MODEL_ID`` and ``SB_CONFIG_BT_FAST_PAIR_ANTI_SPOOFING_PRIVATE_KEY`` Kconfig options.
     * The automatically generated ``bt_fast_pair`` partition definition (in the :file:`subsys/partition_manager/pm.yml.bt_fast_pair` file) to work correctly when building with TF-M.
+    * The behavior of the :c:member:`bt_fast_pair_fmdn_info_cb.provisioning_state_changed` callback.
+      The callback no longer reports the initial provisioning state after the Fast Pair subsystem is enabled with the :c:func:`bt_fast_pair_enable` function call.
+      See the :ref:`migration guide <migration_3.0_recommended>` for mandatory changes and the :ref:`ug_bt_fast_pair_gatt_service_fmdn_info_callbacks_provisioning_state` section in the Fast Pair integration guide for the description on how to track the FMDN provisioning state with the new approach.
 
   * Removed the sysbuild control over the :kconfig:option:`CONFIG_BT_FAST_PAIR` Kconfig option that is defined in the main (default) image.
     Sysbuild no longer sets the value of this Kconfig option.