DOC-5711 DOC-5712 DOC-5713 DOC-5714 DOC-5716 Smart client handoffs docs

[andy-stark-redis]

Draft of docs for Smart client handoffs (aka Seamless client experience, aka Hitless upgrades). I believe all the clients that will initially support this are in beta versions or still in development, so things are likely to change before release.

All feedback is welcome, but a few particular things to think about are:

• "SCE" seems a good abbreviation to use, but I've not officially seen it anywhere.
• The client APIs provide options to set the endpoint type, but I'm not clear about whether this is useful to add to the main docs (ie, do most users have any need to do it?) If it's important, then I'll add it in, of course.
• I've mentioned that Redis Cloud enables SCE by default, but the only method I've seen to enable it in RS is via a REST API call. If we want to publish these docs for the beta versions of SCE then maybe we should give the details of the REST API call. However, I'm guessing there will be a command or config option to enable this for the final release.
• Do we need docs for the CLIENT MAINT_NOTIFICATIONS command?

[github-actions]

Staging links:
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/go/connect/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/go/produsage/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/lettuce/connect/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/lettuce/produsage/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/nodejs/connect/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/nodejs/produsage/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/patterns/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/redis-py/connect/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/redis-py/produsage/
https://redis.io/docs/staging/DOC-5712-python-seamless-section/develop/clients/sch/

[github-actions]

DOC-5712

[dwdougherty]

Generally LGTM. Answers:

• "SCE" seems a good abbreviation to use, but I've not officially seen it anywhere. [DWD] works for me.
• Do we need docs for the CLIENT MAINT_NOTIFICATIONS command? [DWD] no such command AFAIK.

[andy-stark-redis]

@dwdougherty Thanks for the review! I'm not sure if the command is actually useful from the CLI, so we might not end up documenting it.

[dmaier-redislabs]

@andy-stark-redis We aligned the client libs in regards to the parameter names. This means that the public API for this feature changed quite a bit. Please sync with Elena Kolevska about it.