Refactor environment handling logic to separate a server from the environment handler itself

This change makes the environment handling logic execute independent of the server itself and should make it much easier for people to contribute changes and additional environment handlers down the road without polluting the server object even more.

There is still a lot of work to do on this front to make things easier to work with, and there are some questionable design decisions at play I'm sure.

Welcome to additional modifications and cleanup to make this code easier to reason about and work with.

server/loader.go

@@ -7,6 +7,8 @@ import (
 	"github.com/patrickmn/go-cache"
 	"github.com/pkg/errors"
 	"github.com/pterodactyl/wings/api"
+	"github.com/pterodactyl/wings/environment"
+	"github.com/pterodactyl/wings/environment/docker"
 	"os"
 	"runtime"
 	"time"
@@ -87,21 +89,24 @@ func FromConfiguration(data *api.ServerConfigurationResponse) (*Server, error) {
 		return nil, err
 	}
 
-	s.AddEventListeners()
+	s.cache = cache.New(time.Minute*10, time.Minute*15)
+	s.Archiver = Archiver{Server: s}
+	s.Filesystem = Filesystem{Server: s}
 
 	// Right now we only support a Docker based environment, so I'm going to hard code
 	// this logic in. When we're ready to support other environment we'll need to make
 	// some modifications here obviously.
-	if err := NewDockerEnvironment(s); err != nil {
-		return nil, err
+	envCfg := environment.NewConfiguration(s.Mounts(), s.cfg.Allocations, s.cfg.Build, s.cfg.EnvVars)
+	meta := docker.Metadata{
+		Invocation: s.Config().Invocation,
+		Image:      s.Config().Container.Image,
 	}
 
-	s.cache = cache.New(time.Minute*10, time.Minute*15)
-	s.Archiver = Archiver{
-		Server: s,
-	}
-	s.Filesystem = Filesystem{
-		Server: s,
+	if env, err := docker.New(s.Id(), &meta, envCfg); err != nil {
+		return nil, err
+	} else {
+		s.Environment = env
+		s.StartEventListeners()
 	}
 
 	// Forces the configuration to be synced with the panel.