Add session discovery and template support

internal/config/defaults.go

@@ -5,6 +5,9 @@ package config
 const (
 	DefaultPipelineConfigPathUsrLocal = "/usr/local/etc/narratio/pipeline.yml"
 	DefaultPipelineConfigPathEtc      = "/etc/narratio/pipeline.yml"
+	DefaultSessionConfigPathLocal     = "./session.yml"
+	DefaultSessionConfigPathUsrLocal  = "/usr/local/etc/narratio/session.yml"
+	DefaultSessionConfigPathEtc       = "/etc/narratio/session.yml"
 )
 
 // DefaultPipelineConfigSearchPaths defines the default search order for
@@ -16,3 +19,14 @@ var DefaultPipelineConfigSearchPaths = []string{
 	DefaultPipelineConfigPathUsrLocal,
 	DefaultPipelineConfigPathEtc,
 }
+
+// DefaultSessionConfigSearchPaths defines the default search order for
+// session.yml when callers do not provide an explicit path.
+//
+// Keep this in a variable so future defaults can be extended without changing
+// call sites.
+var DefaultSessionConfigSearchPaths = []string{
+	DefaultSessionConfigPathLocal,
+	DefaultSessionConfigPathUsrLocal,
+	DefaultSessionConfigPathEtc,
+}