Support Redis 8

[tylerhutcherson]

This PR adds testing support for Redis 8 (currently redis:8.0-M03 from Docker) to our GitHub Actions pipeline. Overall, our entire test suite passed against Redis 8 with one notable exception:

Breaking Change in Redis 8, Dialect 2 Only
When a search query references a field that is not present in the index schema, Redis 8 now raises:

redis.exceptions.ResponseError: Unknown field at offset NN near <unknown-field-name>

Previously (and in other dialects), Redis would allow such queries but return empty results. This new behavior is arguably more correct, but it breaks a test that expects an empty result when searching on a non-indexed field.

Context and Discussion

A single test failed where our code intentionally queries a field not in the index, expecting empty results. With Redis 8, Dialect 2, this now raises an error.
The team discussed whether to:

• Adjust the test to skip or otherwise handle this new behavior (since querying a non-indexed field arguably should be an error).
• Catch and raise a more user-friendly message in our library. The Redis error text can be cryptic, so providing a clearer explanation to users might be beneficial.

Decision

• Testing: We will proceed with adding Redis 8 to our CI matrix.
• The Failing Test: We will update this test to either skip on Redis 8 or handle the error more gracefully.
• Error Messaging: We may consider adding a better exception message so that developers get a more understandable error when they inadvertently query non-indexed fields. But this will go in a different PR.

[rbs333]

👍