wip: account details from az and the token

internal/provider/provider.go

@@ -184,3 +184,17 @@ type File struct {
 	Line int    // 1-based; 0 for the top
 	Sops string // the sops command to edit it with; empty for a plain file
 }
+
+// Accounts is implemented by providers that can describe the identity
+// they use, from what they have locally: for the Details pane on the
+// provider's row. ok is false when there's nothing to say.
+type Accounts interface {
+	Account() (Account, bool)
+}
+
+// Account describes a signed-in identity.
+type Account struct {
+	Fields []Attr
+	// Copy is what y copies on the provider's row, named CopyLabel.
+	Copy, CopyLabel string
+}