Move metadata plugin registration to seperate package

Signed-off-by: Derek McGowan <derek@mcg.dev>

services/server/config/config.go

@@ -168,44 +168,6 @@ type ProxyPlugin struct {
 	Address string `toml:"address"`
 }
 
-// BoltConfig defines the configuration values for the bolt plugin, which is
-// loaded here, rather than back registered in the metadata package.
-type BoltConfig struct {
-	// ContentSharingPolicy sets the sharing policy for content between
-	// namespaces.
-	//
-	// The default mode "shared" will make blobs available in all
-	// namespaces once it is pulled into any namespace. The blob will be pulled
-	// into the namespace if a writer is opened with the "Expected" digest that
-	// is already present in the backend.
-	//
-	// The alternative mode, "isolated" requires that clients prove they have
-	// access to the content by providing all of the content to the ingest
-	// before the blob is added to the namespace.
-	//
-	// Both modes share backing data, while "shared" will reduce total
-	// bandwidth across namespaces, at the cost of allowing access to any blob
-	// just by knowing its digest.
-	ContentSharingPolicy string `toml:"content_sharing_policy"`
-}
-
-const (
-	// SharingPolicyShared represents the "shared" sharing policy
-	SharingPolicyShared = "shared"
-	// SharingPolicyIsolated represents the "isolated" sharing policy
-	SharingPolicyIsolated = "isolated"
-)
-
-// Validate validates if BoltConfig is valid
-func (bc *BoltConfig) Validate() error {
-	switch bc.ContentSharingPolicy {
-	case SharingPolicyShared, SharingPolicyIsolated:
-		return nil
-	default:
-		return fmt.Errorf("unknown policy: %s: %w", bc.ContentSharingPolicy, errdefs.ErrInvalidArgument)
-	}
-}
-
 // Decode unmarshals a plugin specific configuration by plugin id
 func (c *Config) Decode(p *plugin.Registration) (interface{}, error) {
 	id := p.URI()