added defaults for track and stop variant configuration (tensorzero#4324)

Author: virajmehta

tensorzero-core/src/experimentation/track_and_stop/mod.rs

@@ -256,14 +256,37 @@ impl Nursery {
 pub struct UninitializedTrackAndStopConfig {
     metric: String,
     candidate_variants: Vec<String>,
+    #[serde(default)]
     fallback_variants: Vec<String>,
+    #[serde(default = "default_min_samples_per_variant")]
     min_samples_per_variant: u64,
+    #[serde(default = "default_delta")]
     delta: f64,
+    #[serde(default)]
     epsilon: f64,
+    #[serde(default = "default_update_period_s")]
     update_period_s: u64,
+    #[serde(default = "default_min_prob")]
     min_prob: Option<f64>,
 }
 
+fn default_min_samples_per_variant() -> u64 {
+    10
+}
+
+fn default_delta() -> f64 {
+    0.05
+}
+
+fn default_update_period_s() -> u64 {
+    300
+}
+
+#[expect(clippy::unnecessary_wraps)]
+fn default_min_prob() -> Option<f64> {
+    Some(1e-6)
+}
+
 impl UninitializedTrackAndStopConfig {
     pub fn load(
         self,