feat(bsr): Define stubs for meta structures

These are used to provide the metadata about a session or connection
when writing a BSR and will be written to the corresponding .meta files
within a BSR.

internal/bsr/bsr.go

@@ -0,0 +1,14 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package bsr
+
+// SessionMeta contains metadata about a session in a BSR.
+type SessionMeta struct {
+	Id string
+}
+
+// ConnectionMeta contains metadata about a connection in a BSR.
+type ConnectionMeta struct {
+	Id string
+}