Allow whitelisting by regexp or wildcard expressions in dynamic config frontend.validSearchAttributes

[charlese-instaclustr]

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Currently, adding a custom search attribute for advanced visibility requires whitelisting the attribute key in the dynamic config of each node in a multi-node Cadence setup. This requires a potentially significant amount of manual intervention every time a new attribute is introduced. This ticket is to suggest allowing whitelisting keys via regexp or wildcard-containing expressions in the dynamic config frontend.validSearchAttributes property, such that adding one expression here could serve to whitelist querying a whole collection of keys.

Proposed Solution
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Currently, the function queryValidator.go#isValidSearchAttributes seeks an exact string match between the query key and an entry in the frontend.validSearchAttributes list. Instead, the function could allow for a regexp expression match or similar.

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[charlese-instaclustr]

Cancelling issue in favour of #4948 which is proposing a preferable solution to the same core problem, more discussion in that issue.