Breaking Changes:

All asynchronous callbacks now have both a status member and a coap_rsp_code member to replace the response member. All of the same information remains accessible. Update callback functions to match the new declaration and change any response->status checks to status.
golioth_ota_download_component() has a new uint32_t *next_block_idx parameter. Use this to resume block download. Set to NULL to use previous functionality in existing code.
The parameters for ota_component_block_write_cb() have changed to include block_buffer_len for the actual length of data and negotiated_block_size to indicate the maximum block size (may be used along with block_idx to calculate a byte offset).
golioth_ota_component->hash is now stored as an array of bytes instead of as a hex string.

Highlights:

ESP-IDF: optional ipv6 support enabled by CONFIG_LIBCOAP_ENABLE_IPV6_SUPPORT
LightDB/OTA/RPC: log message when an error response is received from server
CoAP: Server-negotiated block size for blockwise uploads
CoAP: optionally call a set_cb callback at the end of a blockwise upload operation
OTA: ability to resume a component download
golioth_sys_sha256_*() API for calculating OTA component hash
CONFIG_GOLIOTH_OTA to enable OTA component separately from fw_update component
Numerous hardware-in-the-loop (HIL) testing improvements for both code samples and integration tests

Certificates: Replace ISRG Root X2 CA certificate with Golioth Root X1 CA certificate.
Zephyr: Samples: kconfig and devicetree settings common to an SoC moved from boards directory to socs directory.

Zephyr: Golioth coap client log messages now honor changes to the logging level.
Zephyr: Fixed off-by-one error in Golioth backend logging message length limit.
Zephyr: Connection ID is now properly enabled by Kconfig setting.
Zephyr: Run user callbacks when cancelling requests.
Linux: Error checks and max PEM size for certificate_auth sample.

OTA compression was removed as the feature is currently unsupported on the servers side.
Golioth Basics sample removed from Zephyr and ESP-IDF. Existing per-feature sample code for these platforms covers everything demonstrated in that sample.

[Zephyr only] examples won't build for esp32_devkitc_wrover with support for certificates due to bugs in Zephyr that prevent all RAM banks from being made available to the application.