Add graphql query for retrieving imgSummary based on repo:tag image id. (#814)

Refactor Image GqlResolver to better suit GetManifest.
Changed GetManifest to also return digest.

Signed-off-by: Bogdan BIVOLARU <104334+bogdanbiv@users.noreply.github.com>

errors/errors.go

@@ -18,7 +18,7 @@ var (
 	ErrBadBlobDigest           = errors.New("blob: bad blob digest")
 	ErrUnknownCode             = errors.New("error: unknown error code")
 	ErrBadCACert               = errors.New("tls: invalid ca cert")
-	ErrBadUser                 = errors.New("ldap: non-existent user")
+	ErrBadUser                 = errors.New("auth: non-existent user")
 	ErrEntriesExceeded         = errors.New("ldap: too many entries returned")
 	ErrLDAPEmptyPassphrase     = errors.New("ldap: empty passphrase")
 	ErrLDAPBadConn             = errors.New("ldap: bad connection")
@@ -32,7 +32,7 @@ var (
 	ErrInvalidArgs             = errors.New("cli: Invalid Arguments")
 	ErrInvalidFlagsCombination = errors.New("cli: Invalid combination of flags")
 	ErrInvalidURL              = errors.New("cli: invalid URL format")
-	ErrUnauthorizedAccess      = errors.New("cli: unauthorized access. check credentials")
+	ErrUnauthorizedAccess      = errors.New("auth: unauthorized access. check credentials")
 	ErrCannotResetConfigKey    = errors.New("cli: cannot reset given config key")
 	ErrConfigNotFound          = errors.New("cli: config with the given name does not exist")
 	ErrNoURLProvided           = errors.New("cli: no URL provided in argument or via config")
@@ -58,4 +58,5 @@ var (
 	ErrBadType                 = errors.New("core: invalid type")
 	ErrParsingHTTPHeader       = errors.New("routes: invalid HTTP header")
 	ErrBadRange                = errors.New("storage: bad range")
+	ErrBadLayerCount           = errors.New("manifest: layers count doesn't correspond to config history")
 )