New config `rdb-version-check` with values:
* `strict`: Reject future RDB versions.
* `relaxed`: Try parsing future RDB versions and fail only when an
unknown RDB opcode or type is encountered.
This can make it possible for Valkey 8.1 to try read a dump from for
example Valkey 9.0 or later on a best-effort basis. The conditions for
when this is expected to work can be defined when the future Valkey
versions are released. Loading is expected to fail in the following
cases:
* If the data set contains any new key types or other data elements not
supported by the current version.
* If the RDB contains new representations or encodings of existing key
types or other data elements.
This change also prepares for the next RDB version bump. A range of RDB
versions (12-79) is reserved, since it's expected to be used by foreign
software RDB versions, so Valkey will not accept versions in this range
even with the `relaxed` version check. The DUMP/RESTORE format has no
magic string; only the RDB version number.
This change also prepares for the magic string to change from REDIS to
VALKEY next time we bump the RDB version.
Related to #1108.
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Signed-off-by: Viktor Söderqvist <viktor.soderqvist@est.tech>
Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>
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