feat: Server support for Android push notifications (#236)

* feat: Server support for Android push notifications

* Address review comments

backend/src/qs/client_record.rs

@@ -295,6 +295,14 @@ impl QsClientRecord {
                                         "Push notification failed because the JWT token could not be created: {}",
                                         e
                                     ),
+                                    PushNotificationError::OAuthError(e) => tracing::error!(
+                                        "Push notification failed because of an OAuth error: {}",
+                                        e
+                                    ),
+                                    PushNotificationError::InvalidConfiguration(e) => tracing::error!(
+                                        "Push notification failed because of an invalid configuration: {}",
+                                        e
+                                    ),
                                 }
                                     }
                                 }

backend/src/qs/mod.rs

@@ -165,6 +165,10 @@ pub enum PushNotificationError {
     UnsupportedType,
     /// The JWT token for APNS could not be created.
     JwtCreationError(String),
+    /// OAuth error.
+    OAuthError(String),
+    /// Configuration error.
+    InvalidConfiguration(String),
 }
 
 #[async_trait]

backend/src/settings.rs

@@ -12,6 +12,9 @@ pub struct Settings {
     // If this isn't present, the provider will not send push notifications to
     // apple devices.
     pub apns: Option<ApnsSettings>,
+    // If this isn't present, the provider will not send push notifications to
+    // android devices.
+    pub fcm: Option<FcmSettings>,
 }
 
 /// Configuration for the application.
@@ -33,6 +36,12 @@ pub struct DatabaseSettings {
     pub cacertpath: Option<String>,
 }
 
+#[derive(Debug, Deserialize, Clone)]
+pub struct FcmSettings {
+    // The path to the service account key file.
+    pub path: String,
+}
+
 #[derive(Debug, Deserialize, Clone)]
 pub struct ApnsSettings {
     pub keyid: String,

server/Cargo.toml

@@ -25,6 +25,7 @@ phnxbackend = { path = "../backend" }
 phnxtypes = { path = "../types" }
 actix-web = "^4.0"
 serde = "1"
+serde_json = "1.0"
 config = "0.14"
 async-trait = "0.1.74"
 actix-web-actors = "4.2.0"
@@ -39,6 +40,7 @@ tracing-bunyan-formatter = "0.3"
 tracing-actix-web = "0.7"
 jsonwebtoken = "9"
 opaque-ke = { version = "3.0.0-pre.5", features = ["argon2"] }
+zeroize = "1.8.1"
 
 # Workspace dependencies
 tls_codec = { workspace = true }