Add prune retention planning

internal/config/load_test.go

@@ -39,6 +39,9 @@ pipelines:
 	if got, want := destination.State.Mode, StateModeSingleOwner; got != want {
 		t.Fatalf("state mode default = %q, want %q", got, want)
 	}
+	if destination.Retention.Prune.Enabled {
+		t.Fatal("retention.prune.enabled default = true, want false")
+	}
 	if cfg.Secrets.Directory != "" {
 		t.Fatalf("secrets.directory = %q, want empty", cfg.Secrets.Directory)
 	}
@@ -228,6 +231,36 @@ pipelines:
 	}
 }
 
+func TestLoadFileAcceptsRetentionPruneConfig(t *testing.T) {
+	cfg := loadConfig(t, `
+pipelines:
+  - id: reports
+    source:
+      backend: local
+      path: /source
+    destinations:
+      - id: archive
+        backend: local
+        path: /archive
+        retention:
+          prune:
+            enabled: true
+            older_than: 168h
+            keep_latest: 3
+`)
+
+	prune := cfg.Pipelines[0].Destinations[0].Retention.Prune
+	if !prune.Enabled {
+		t.Fatal("retention.prune.enabled = false, want true")
+	}
+	if prune.OlderThan == nil || prune.OlderThan.String() != "168h0m0s" {
+		t.Fatalf("retention.prune.older_than = %v, want 168h", prune.OlderThan)
+	}
+	if prune.KeepLatest == nil || *prune.KeepLatest != 3 {
+		t.Fatalf("retention.prune.keep_latest = %v, want 3", prune.KeepLatest)
+	}
+}
+
 func TestLoadFileAcceptsFixedPathMapping(t *testing.T) {
 	cfg := loadConfig(t, `
 pipelines:
@@ -705,6 +738,7 @@ pipelines: [{id: reports, source: {backend: http_upload, max_upload_size: 20XB},
 pipelines: [{id: reports, source: {backend: http_upload, max_upload_size: 0B}, destinations: [{id: archive, backend: local, path: /archive}]}]`,
 		"server duration":         `server: {http: {retention: forever}}`,
 		"zero server duration":    `server: {http: {retention: 0s}}`,
+		"prune duration":          `pipelines: [{id: reports, source: {backend: local, path: /source}, destinations: [{id: archive, backend: local, path: /archive, retention: {prune: {enabled: true, older_than: forever}}}]}]`,
 		"missing upload tokens":   `pipelines: [{id: reports, source: {backend: http_upload}, destinations: [{id: archive, backend: local, path: /archive}]}]`,
 		"destination http upload": `pipelines: [{id: reports, source: {backend: local, path: /source}, destinations: [{id: ingest, backend: http_upload}]}]`,
 		"literal token": `upload_tokens: [{id: reporter, token: secret, token_env: UPLOAD_TOKEN, allow_pipelines: [reports]}]