feat(feature-flags): add posthog-server user agent for server-side SDK detection

rust/feature-flags/src/handler/types.rs

@@ -96,6 +96,8 @@ pub enum Library {
     PosthogReactNative,
     /// posthog-flutter SDK
     PosthogFlutter,
+    /// posthog-server SDK (deprecated: users are migrating to posthog-java)
+    PosthogServer,
     /// Unknown or unrecognized SDK
     Other,
 }
@@ -120,6 +122,7 @@ impl Library {
             Library::PosthogIos => "posthog-ios",
             Library::PosthogReactNative => "posthog-react-native",
             Library::PosthogFlutter => "posthog-flutter",
+            Library::PosthogServer => "posthog-server",
             Library::Other => "other",
         }
     }
@@ -141,6 +144,7 @@ impl Library {
         Library::PosthogIos,
         Library::PosthogReactNative,
         Library::PosthogFlutter,
+        Library::PosthogServer,
     ];
 }
 
@@ -236,6 +240,8 @@ mod tests {
     #[case("posthog-java/1.2.0", Library::PosthogJava)]
     #[case("posthog-dotnet/1.0.0", Library::PosthogDotnet)]
     #[case("posthog-elixir/0.2.0", Library::PosthogElixir)]
+    #[case("posthog-server/1.0.0", Library::PosthogServer)]
+    #[case("posthog-server/3.2.1 (Android SDK)", Library::PosthogServer)]
     // Client-side SDKs
     #[case("posthog-js/1.88.0", Library::PosthogJs)]
     #[case("posthog-android/3.0.0", Library::PosthogAndroid)]
@@ -322,6 +328,7 @@ mod tests {
     #[case(Library::PosthogIos, "posthog-ios")]
     #[case(Library::PosthogReactNative, "posthog-react-native")]
     #[case(Library::PosthogFlutter, "posthog-flutter")]
+    #[case(Library::PosthogServer, "posthog-server")]
     #[case(Library::Other, "other")]
     fn test_library_display(#[case] library: Library, #[case] expected: &str) {
         assert_eq!(library.to_string(), expected);
@@ -341,6 +348,7 @@ mod tests {
     #[case(Library::PosthogIos, "\"posthog-ios\"")]
     #[case(Library::PosthogReactNative, "\"posthog-react-native\"")]
     #[case(Library::PosthogFlutter, "\"posthog-flutter\"")]
+    #[case(Library::PosthogServer, "\"posthog-server\"")]
     #[case(Library::Other, "\"other\"")]
     fn test_library_serialization(#[case] library: Library, #[case] expected_json: &str) {
         assert_eq!(serde_json::to_string(&library).unwrap(), expected_json);

rust/feature-flags/src/utils/user_agent.rs

@@ -98,6 +98,8 @@ impl UserAgentInfo {
             "node" => ("posthog-node", RuntimeType::Server),
             "dotnet" => ("posthog-dotnet", RuntimeType::Server),
             "elixir" => ("posthog-elixir", RuntimeType::Server),
+            // Deprecated: posthog-server users are migrating to posthog-java
+            "server" => ("posthog-server", RuntimeType::Server),
             // Client-side SDKs (mobile and browser)
             "js" => ("posthog-js", RuntimeType::Client),
             "android" => ("posthog-android", RuntimeType::Client),
@@ -231,6 +233,18 @@ mod tests {
         Some("0.2.0"),
         RuntimeType::Server
     )]
+    #[case(
+        "posthog-server/1.0.0",
+        Some("posthog-server"),
+        Some("1.0.0"),
+        RuntimeType::Server
+    )]
+    #[case(
+        "posthog-server/3.2.1 (Android SDK)",
+        Some("posthog-server"),
+        Some("3.2.1"),
+        RuntimeType::Server
+    )]
     #[case(
         "posthog-js/1.88.0",
         Some("posthog-js"),
@@ -341,6 +355,7 @@ mod tests {
     #[case(Some("posthog-node/2.2.0"), "posthog-node")]
     #[case(Some("posthog-dotnet/1.0.0"), "posthog-dotnet")]
     #[case(Some("posthog-elixir/0.2.0"), "posthog-elixir")]
+    #[case(Some("posthog-server/1.0.0"), "posthog-server")]
     #[case(
         Some("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36"),
         "browser"
@@ -366,6 +381,7 @@ mod tests {
     #[case("posthog-python/3.0.0", Some("posthog-python"))]
     #[case("posthog-node/1.2.3", Some("posthog-node"))]
     #[case("posthog-android/3.0.0", Some("posthog-android"))]
+    #[case("posthog-server/1.0.0", Some("posthog-server"))]
     #[case("Mozilla/5.0 (Windows NT 10.0; Win64; x64)", Some("web"))]
     #[case("Chrome/120.0.0.0 Safari/537.36", Some("web"))]
     #[case("curl/7.68.0", None)]