feat: Implement mailer service for sending emails

src/service/Cargo.toml

@@ -123,6 +123,7 @@ blurhash.workspace = true
 blurhash.optional = true
 recaptcha-verify = { version = "0.2.0", default-features = false }
 yansi.workspace = true
+lettre.workspace = true
 
 [target.'cfg(all(unix, target_os = "linux"))'.dependencies]
 sd-notify.workspace = true