feat: Add backend rate limit route

src/main/kotlin/app/revanced/api/configuration/repository/BackendRepository.kt

@@ -41,7 +41,6 @@ abstract class BackendRepository internal constructor(
          * @property bio The bio of the member.
          * @property gpgKeys The GPG key of the member.
          */
-        @Serializable
         class BackendMember(
             override val name: String,
             override val avatarUrl: String,
@@ -110,6 +109,19 @@ abstract class BackendRepository internal constructor(
         }
     }
 
+    /**
+     * The rate limit of the backend.
+     *
+     * @property limit The limit of the rate limit.
+     * @property remaining The remaining requests of the rate limit.
+     * @property reset The date and time the rate limit resets.
+     */
+    class BackendRateLimit(
+        val limit: Int,
+        val remaining: Int,
+        val reset: LocalDateTime,
+    )
+
     /**
      * Get a release of a repository.
      *
@@ -140,4 +152,11 @@ abstract class BackendRepository internal constructor(
      * @return The members.
      */
     abstract suspend fun members(organization: String): Set<BackendOrganization.BackendMember>
+
+    /**
+     * Get the rate limit of the backend.
+     *
+     * @return The rate limit.
+     */
+    abstract suspend fun rateLimit(): BackendRateLimit?
 }

src/main/kotlin/app/revanced/api/configuration/routing/routes/ApiRoute.kt

@@ -1,5 +1,6 @@
 package app.revanced.api.configuration.routing.routes
 
+import app.revanced.api.configuration.respondOrNotFound
 import app.revanced.api.configuration.services.ApiService
 import app.revanced.api.configuration.services.AuthService
 import io.ktor.http.*
@@ -28,6 +29,10 @@ internal fun Route.rootRoute() {
         }
     }
 
+    get("backend/rate_limit") {
+        call.respondOrNotFound(apiService.rateLimit())
+    }
+
     authenticate("basic") {
         get("token") {
             call.respond(authService.newToken())

src/main/kotlin/app/revanced/api/configuration/schema/APISchema.kt

@@ -106,3 +106,10 @@ class APILatestAnnouncement(
 class APIAnnouncementArchivedAt(
     val archivedAt: LocalDateTime,
 )
+
+@Serializable
+class APIRateLimit(
+    val limit: Int,
+    val remaining: Int,
+    val reset: LocalDateTime,
+)

src/main/kotlin/app/revanced/api/configuration/services/ApiService.kt

@@ -42,4 +42,8 @@ internal class ApiService(
 
         )
     }
+
+    suspend fun rateLimit() = backendRepository.rateLimit()?.let {
+        APIRateLimit(it.limit, it.remaining, it.reset)
+    }
 }