Move IsDeprecatedRPCEnabled to rpc/util, rm redundant rpcEnableDeprecated #27322

CI builds currently fail when IsDeprecatedRPCEnabled() is called from wallet RPCs with "Undefined reference to IsDeprecatedRPCEnabled in libbitcoin_wallet".

Fix the issue by moving IsDeprecatedRPCEnabled() from rpc/server to rpc/util, thereby moving it from node to common to be picked up by libbitcoin_wallet (see doc/design/librairies.md and src/Makefile.am).

This move allows us to drop the redundant rpcEnableDeprecated() method. Per the comment in src/interfaces/chain.h::L107 from #15639 we would like to remove these, and this function doesn't seem constrained by the mentioned HTTP port requirement, nor needed if IsDeprecatedRPCEnabled is in common rather than node.

This allows having only one call for this functionality and avoids developer confusion and head-scratching.

If it is preferred to keep all of them, this pull could alternatively document the use of these different methods for future developers doing a deprecation.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #27757 (rpc: remove deprecated "warning" field from {create,load,restore,unload}wallet by theStack)
• #27101 (Support JSON-RPC 2.0 when requested by client by pinheadmz)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

lgtm

Maybe explain that this moves it from node to common?

PR description and commit message updated per #27322 (comment) (thanks @MarcoFalke).

Actually, on a second though. Any reason why you can't just call rpcEnableDeprecated?

Any reason why you can't just call rpcEnableDeprecated?

Good question. Looking at it, maybe we can remove it? Per this comment in src/interfaces/chain.h::L107 from #15639 we would like to remove these, and this function doesn't seem constrained by the mentioned HTTP port requirement or needed if IsDeprecatedRPCEnabled is in common rather than node (the first commit here). @ryanofsky wdyt?

//! * The handleRpc, registerRpcs, rpcEnableDeprecated methods and other RPC
//!   methods can go away if wallets listen for HTTP requests on their own
//!   ports instead of registering to handle requests on the node HTTP port.

Rebased 😃

crACK 9ed9b50068a3cbcf48264d814ffe73e0b9ed10b4

nit: s/librairies/libraries in 1a1f3518ed4eb2b18c63d98fbdca10a2cda8bf1e message

Is gArgs guaranteed to be identical in different processes? If not, it would be good to explain why this behavior change is intentional. If yes, it would be good to explain as well.

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🐙 This pull request conflicts with the target branch and needs rebase.

Needs a rebase, if still relevant, and the question above also needs addressing.

Closing this as it has not had any activity in a while. If you are interested in continuing work on this, please leave a comment so that it can be reopened.