feat: support Zephyr 4.2.0

* replace deprecated swap mode option
From https://docs.zephyrproject.org/latest/releases/migration-guide-4.1.html:
```
The Kconfig ``SB_CONFIG_MCUBOOT_MODE_SWAP_WITHOUT_SCRATCH`` has been deprecated and replaced
with ``SB_CONFIG_MCUBOOT_MODE_SWAP_USING_MOVE``, applications should be updated to select this
new symbol if they were selecting the old symbol.
```

Note that this will still allow us to build with older versions, as the
MCUboot options set in mender-mcu's Kconfig are merely there for verbosity

* return int in response callbacks
This is needed in order to use Zephyr 4.2.0

From https://docs.zephyrproject.org/latest/releases/migration-guide-4.2.html:
```
The http_response_cb_t HTTP client response callback signature has changed.
The callback function now returns int instead of void. This allows the
application to abort the HTTP connection. Existing applications need to
update their response callback implementations. To retain current behavior,
simply return 0 from the callback.
```

In order to not break backwards compatibility we use Zephyr's `ZEPHYR_VERSION`
and `ZEPHYR_VERSION_CODE` to define macros that return void on versions
below 4.2.0 and int on newer versions.

Ticket: MEN-8638
Changelog: Title

Signed-off-by: Daniel Skinstad Drabitzius <daniel.drabitzius@northern.tech>

Author: danielskinstad

README.md

@@ -51,7 +51,7 @@ here for more in-depth information.
 ### Compatibility
 | Zephyr OS version |
 |-------------------|
-| v4.0.0            |
+| v4.2.0            |
 
 ### Boards
 The reference board for `mender-mcu` is the [ESP32-S3-DevKitC](https://docs.zephyrproject.org/latest/boards/espressif/esp32s3_devkitc/doc/index.html).
@@ -151,7 +151,8 @@ MCUboot. The following link will filter the officially supported boards that als
 The Update Module requires a swap algorithm in order to allow rollbacks to revert to the previous image.
 The [MCUboot documentation](https://docs.mcuboot.com/readme-zephyr.html) recommends against using the
 `swap-using-scratch algorithm`, which also requires its own `scratch_partition`. We therefore require
-`MCUBOOT_MODE_SWAP_WITHOUT_SCRATCH` to be enabled in order to use the Update Module.
+`MCUBOOT_MODE_SWAP_USING_MOVE` (`MCUBOOT_MODE_SWAP_WITHOUT_SCRATCH` for Zephyr versions below 4.1) to be
+enabled in order to use the Update Module.
 
 #### Update Modules State Machine
 

src/platform/net/zephyr/http.c

@@ -27,6 +27,15 @@
 
 #include "net.h"
 
+/* Zephyr versions 4.2.0 and above return int, versions below 4.2.0 return void */
+#if (ZEPHYR_VERSION_CODE < ZEPHYR_VERSION(4, 2, 0))
+#define HTTP_CALLBACK_RETURN_VALUE
+#define HTTP_CALLBACK_RETURN_TYPE void
+#else
+#define HTTP_CALLBACK_RETURN_VALUE 0
+#define HTTP_CALLBACK_RETURN_TYPE  int
+#endif
+
 /**
  * @brief HTTP User-Agent
  */
@@ -58,16 +67,18 @@ static mender_http_config_t http_config;
  * @param response HTTP response structure
  * @param final_call Indicate final call
  * @param user_data User data, used to retrieve request context data
+ * @return HTTP_CALLBACK_RETURN_VALUE, 0 if Zephyr >= 4.2.0, void otherwise
  */
-static void http_response_cb(struct http_response *response, enum http_final_call final_call, void *user_data);
+static HTTP_CALLBACK_RETURN_TYPE http_response_cb(struct http_response *response, enum http_final_call final_call, void *user_data);
 
 /**
  * @brief HTTP artifact response callback, invoked to handle data received
  * @param response HTTP response structure
  * @param final_call Indicate final call
  * @param user_data User data, used to retrieve request context data
+ * @return HTTP_CALLBACK_RETURN_VALUE, 0 if Zephyr >= 4.2.0, void otherwise
  */
-static void artifact_response_cb(struct http_response *response, enum http_final_call final_call, void *user_data);
+static HTTP_CALLBACK_RETURN_TYPE artifact_response_cb(struct http_response *response, enum http_final_call final_call, void *user_data);
 
 /**
  * @brief Convert mender HTTP method to Zephyr HTTP client method
@@ -352,7 +363,7 @@ mender_http_exit(void) {
     return MENDER_OK;
 }
 
-static void
+static HTTP_CALLBACK_RETURN_TYPE
 http_response_cb(struct http_response *response, MENDER_ARG_UNUSED enum http_final_call final_call, void *user_data) {
     assert(NULL != response);
     assert(NULL != user_data);
@@ -370,9 +381,10 @@ http_response_cb(struct http_response *response, MENDER_ARG_UNUSED enum http_fin
             mender_log_error("An error occurred, stop reading data");
         }
     }
+    return HTTP_CALLBACK_RETURN_VALUE;
 }
 
-static void
+static HTTP_CALLBACK_RETURN_TYPE
 artifact_response_cb(struct http_response *response, MENDER_ARG_UNUSED enum http_final_call final_call, void *user_data) {
 
     assert(NULL != response);
@@ -390,6 +402,7 @@ artifact_response_cb(struct http_response *response, MENDER_ARG_UNUSED enum http
             mender_log_error("An error occurred, stop reading data");
         }
     }
+    return HTTP_CALLBACK_RETURN_VALUE;
 }
 
 static enum http_method

target/zephyr/Kconfig

@@ -159,7 +159,7 @@ if MENDER_MCU_CLIENT
             # The MCUboot options here do not
             # affect the MCUboot configuration
             select BOOTLOADER_MCUBOOT
-            select MCUBOOT_MODE_SWAP_WITHOUT_SCRATCH
+            select MCUBOOT_MODE_SWAP_USING_MOVE
             select IMG_ENABLE_IMAGE_CHECK
             select IMG_ERASE_PROGRESSIVELY
             select IMG_MANAGER
@@ -168,8 +168,9 @@ if MENDER_MCU_CLIENT
                 The default zephyr-image update module handles full Zephyr images on MCUboot-based devices.
                 The MCUboot options selected here do not actually modify the behavior of the bootloader
                 since it's built separately from the Mender MCU client. `BOOTLOADER_MCUBOOT`
-                and `MCUBOOT_MODE_SWAP_WITHOUT_SCRATCH` (or another swap algorithm) must be enabled in
-                the bootloader configuration, e.g. `sysbuild.conf` if you're using sysbuild.
+                and `MCUBOOT_MODE_SWAP_USING_MOVE (`MCUBOOT_MODE_SWAP_WITHOUT_SCRATCH` for Zephyr versions below 4.1)`
+                (or another swap algorithm) must be enabled in the bootloader configuration, e.g. `sysbuild.conf`
+                if you're using sysbuild.
     endmenu
 
     menuconfig MENDER_ARTIFACT_GENERATE