Offline player fetching improvements

[EpicPlayerA10]

Changes

• getOfflinePlayer now returns CompletableFuture instead of passing Consumer to it. This allows us for better handling any exceptions in commands.
• Changed api for fetching offline player to use official Minecraft API. Why? Because sometimes the previous api didn't have the latest data. For example I had a bug where my friend created new minecraft account and when I tried to add him to maintenance whitelist, then it would show that player does not exists. I tried multiple times, but without success.
• Added the previous API (Ashcon API) as a fallback when mojang API will rate limit you.
• Added option to proxy config fallback-to-offline-uuid to fallback to offline uuid when premium player was not found. Useful on proxy when you have a hybrid setup like: Premium Player -> Online UUID Cracked Player -> Offline UUID
• Fixed bug with players tab-completion in command "/maintenance remove"

[kennytv]

Okay so I just remembered why I used that 3rd party service in the first place - People on server hosting providers kept running into ratelimits due to shared servers/ip ranges, so maybe it should use Mojang services first and then fall back to the previous one if limited

[EpicPlayerA10]

Okay so I just remembered why I used that 3rd party service in the first place - People on server hosting providers kept running into ratelimits due to shared servers/ip ranges, so maybe it should use Mojang services first and then fall back to the previous one if limited

Done