[feature] Add backend for `sdk`

[curetheopensource]

Hello again! I would like to add the backend for SDKMAN!. It has some special features compared to other package managers:

• can install different versions of same SDK (the candidate term is originally used), only the one version per candidate could be set as default (current);
• additionally to the version number, some candidates have the vendor suffix (e.g. 21.0.4-tem for java);
• interactive by default (asks to set the installed candidate as the new default) - the CLI should be either manually configured or installed with additional options;
• the original CLI does not support listing candidates, only theirs versions and the whole list of candidates available for installation;
• traditionally installed for the current user, no sudo permissions needed.

How to implement

• add the new backend named sdk;
• to support different versions, an sdk package name could contain an optional segment, e.g. { package = "java/20.1.4-tem" }. Without it, the latest SDK's default version is being installed (the CLI supports this case);
• it is the user's responsibility to disable interactivity of sdk (a little instruction about non-interactive usage could be added in the readme);
• to find out which SDKs are installed by the manager, lsing directories in $SDKMAN_DIR/candidates could be performed;
• parse the table-ish output from sdk list <candidate>, the output format differs depending on whether the candidate supports vendors or not;
• keep the default candidates' versions by calling sdk default <candidate> <version> in non-interactive mode.

What do think about this feature?

[ripytide]

Nice write up.

metapac has a --no_confirm option which is how we decide whether to make the resulting commands interactive or not by passing the relevant option to the given backend.

I think this will be the first backend that allows installing different versions of the same package. But since each package name / version tuple is unique that seems fine using a "name/version" pattern for each package id.

I found sdk's GitHub issue for a lack of a decent list command hilarious: sdkman/sdkman-cli#466 I think the takeaway is that they are planning on implementing it in the rust rewrite. I'm not sure how far along that is though. Maybe it would be worth waiting until the rust rewrite has the features we need, rather than bodging a solution on the old version of sdk.

[curetheopensource]

@ripytide oh, so there is the native way to get SDKs installed! I did not know about it. Thus, there is no need to access the file system directly, cool! I'll take a closer look at what's going on there, thanks!