Migration guide for OID
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
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+## OID module
+
+The compilation option `MBEDTLS_OID_C` no longer exists. OID tables are included in the build automatically as needed for parsing and writing X.509 data.
+
+Mbed TLS no longer offers interfaces to look up values by OID or OID by enum values (`mbedtls_oid_get_<thing>()` and `mbedtls_oid_get_oid_by_<thing>()`).
+
+The header `<mbedtls/oid.h>` now only provides functions to convert between binary and dotted string OID representations. These functions are now part of `libmbedx509` rather than the crypto library. The function `mbedtls_oid_get_numeric_string()` is guarded by `MBEDTLS_X509_USE_C`, and `mbedtls_oid_from_numeric_string()` by `MBEDTLS_X509_CREATE_C`. The header also still defines macros for OID strings that are relevant to X.509.