Added support for getOfflinePlayer(String) with optional cache

[TheBusyBiscuit]

PaperMC/Paper#4687 has introduced the ability to get an OfflinePlayer by their name without making a web request.

To properly utilise this feature in a Spigot-compatible environment, we currently need to rely on an isPaper and a version check to even see whether one is able to optimize for that.
I think this is a perfect opportunity for a PaperLib implementation.

This is just a basic implementation which was done in a similar manner to how the BlockStateSnapshot is handled.
The boolean makeWebRequest determines whether a web request is allowed. In environments that do not support Bukkit.getOfflinePlayerIfCached(), this boolean is just ignored. Similar to how BlockStateSnapshot will ignore the useSnapshot boolean if unsupported.

Of course, the Bukkit.getOfflinePlayerIfCached() method will not be available in every single 1.16.4-compatible build of Paper I presume, but I am gonna assume the typical "old versions are not supported anyway" situation here for now.
Lemme know if there is anything that should be changed or documented.

[JRoy]

Couple of things plus you're missing the helper method in the PaperLib class (and its javadocs)

[JRoy]

reflection can be used here to check if the profile cache returns null for the given username (UserCache#c#get mapping has been consistent since 1.8.8). That way the makeWebRequest parameter can be respected even if we're on spigot.

(core team may have input on this)

[TheBusyBiscuit]

Hmm, that would certainly be a neat idea.
I will look into it but also wait and see what others think about this.

[TheBusyBiscuit]

So I had a look into it and UserCache#c seems to refer to a static boolean on Spigot 1.16.4 (tested using git-Spigot-05da6fa-b0c6dfe).
So unless, that was a typo the mapping does not seem to be as consistent as expected.
The actual Map<String, UserCacheEntry> is found under UserCache#d on the build I investigated.

There is a UserCache#getProfile(String) method though, which returns a nullable GameProfile for a given username from the cache (unless expired).
I would need to look up how long this method existed though.

Update: UserCache#getProfile(String) has been consistent since CB 1.8 (said class did not exist prior to 1.8). Invoking that method using reflection is definitely our safest option to implement this in a non-Paper environment.
What do you think?

[TheBusyBiscuit]

Thanks for the input!

you're missing the helper method in the PaperLib class (and its javadocs)

Whoops, I somehow completely forgot about that, thanks for spotting it.
I agree with the name changes for the classes as they seem more reflective of the internal logic here, also implemented the reflection-check you suggested for the method. Probably much better than simply relying on people to update their software.