settings: Instanciate only a single instance of the ServiceHandler/Store

Share the same instance between the HTTP and the GRPC service. This is
in preparation for moving the cache of the metadata storage backend to a
go-micro/store based implementation. By sharing the same service instance in
the HTTP and GRPC services we can avoid the usage of global variables for the
caches, which will make the move to the go-micro/store implementation simpler.

services/settings/pkg/store/metadata/cache.go

@@ -11,10 +11,6 @@ import (
 
 var (
 	cachettl = 0
-	// these need to be global instances for now as the `Service` (and therefore the `Store`) are instantiated twice (for grpc and http)
-	// therefore caches need to cover both instances
-	dircache   = initCache(cachettl)
-	filescache = initCache(cachettl)
 )
 
 // CachedMDC is cache for the metadataclient
@@ -99,8 +95,8 @@ func (c *CachedMDC) MakeDirIfNotExist(ctx context.Context, id string) error {
 
 // Init instantiates the caches
 func (c *CachedMDC) Init(ctx context.Context, id string) error {
-	c.dirs = dircache
-	c.files = filescache
+	c.dirs = initCache(cachettl)
+	c.files = initCache(cachettl)
 	return c.next.Init(ctx, id)
 }