Revert "settings: Remove auxiliary Content types where possible (#16744)" (#17768)

This breaks setting `{"scrollbar": {"show":"never"}}`
Release Notes:

- N/A

crates/call/src/call_settings.rs

@@ -4,20 +4,30 @@ use schemars::JsonSchema;
 use serde_derive::{Deserialize, Serialize};
 use settings::{Settings, SettingsSources};
 
-/// Configuration of voice calls in Zed.
-#[derive(Clone, Debug, Default, Deserialize, Serialize, JsonSchema)]
-#[serde(default)]
+#[derive(Deserialize, Debug)]
 pub struct CallSettings {
-    /// Whether the microphone should be muted when joining a channel or a call.
     pub mute_on_join: bool,
-    /// Whether your current project should be shared when joining an empty channel.
     pub share_on_join: bool,
 }
 
+/// Configuration of voice calls in Zed.
+#[derive(Clone, Default, Serialize, Deserialize, JsonSchema, Debug)]
+pub struct CallSettingsContent {
+    /// Whether the microphone should be muted when joining a channel or a call.
+    ///
+    /// Default: false
+    pub mute_on_join: Option<bool>,
+
+    /// Whether your current project should be shared when joining an empty channel.
+    ///
+    /// Default: true
+    pub share_on_join: Option<bool>,
+}
+
 impl Settings for CallSettings {
     const KEY: Option<&'static str> = Some("calls");
 
-    type FileContent = Self;
+    type FileContent = CallSettingsContent;
 
     fn load(sources: SettingsSources<Self::FileContent>, _: &mut AppContext) -> Result<Self> {
         sources.json_merge()