fix eviction policy parsing

Signed-off-by: Alex Chi <iskyzh@gmail.com>

libs/pageserver_api/src/models.rs

@@ -235,7 +235,7 @@ pub struct TenantConfig {
     // Otherwise we'd have to move the types for eviction policy into this package.
     // We might do that once the eviction feature has stabilizied.
     // For now, this field is not even documented in the openapi_spec.yml.
-    #[clap(long, value_parser = clap::value_parser!(serde_json::Value))]
+    #[clap(long, value_parser = parse_json)]
     pub eviction_policy: Option<serde_json::Value>,
     #[clap(long)]
     pub min_resident_size_override: Option<u64>,
@@ -244,6 +244,10 @@ pub struct TenantConfig {
     pub gc_feedback: Option<bool>,
 }
 
+fn parse_json(s: &str) -> Result<serde_json::Value, serde_json::Error> {
+    serde_json::from_str(s)
+}
+
 impl TenantConfig {
     pub fn deserialize_from_settings(settings: HashMap<&str, &str>) -> Result<Self, anyhow::Error> {
         let config = TenantConfig::try_parse_from(
@@ -928,6 +932,15 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_parse_json_field() {
+        let config = vec![(
+            "eviction_policy",
+            "eviction_policy:{\"kind\": \"NoEviction\"}",
+        )];
+        TenantConfig::deserialize_from_settings(config.into_iter().collect()).unwrap();
+    }
+
     #[test]
     fn tenantstatus_activating_serde() {
         let states = [