Update websockets dependency requirements

[ggml1]

Hey!

I have been using this SDK with a uvicorn server. They have recently upgraded the websockets requirements (link), and the version 9.1 includes a fix for a security issue introduced in version 8.

Currently, they require >=9.1, while this SDK requires >=8,<9. It would be awesome if you could also bump your requirements so that we didn't need to pin the uvicorn version and could also benefit from this security fix.

I'd be happy to open a PR to help with the upgrade if needed, but I couldn't quite figure out how the library is used and what code changes might need to be done for this major upgrade.

Category (place an x in each of the [ ])

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.models (UI component builders)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.scim (SCIM API client)
• slack_sdk.rtm (RTM client)
• slack_sdk.signature (Request Signature Verifier)

Requirements

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[seratch]

Hi @ggml1, thanks for sharing this! There is no blocker for upgrading websockets dependency to the latest as it's an optional one. As this is a security update, we set 9.1 as the oldest supported version. I think we can set >=9.1,<10 this time. Your contributions would be appreciated!

[ggml1]

Thanks @seratch! Will open a PR