feat: implement federation list endpoint

modules/admin-server/src/main/kotlin/com/sphereon/oid/fed/server/admin/controllers/SubordinateController.kt

@@ -0,0 +1,19 @@
+package com.sphereon.oid.fed.server.admin.controllers
+
+import com.sphereon.oid.fed.persistence.models.Subordinate
+import com.sphereon.oid.fed.services.SubordinateService
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.PathVariable
+import org.springframework.web.bind.annotation.RequestMapping
+import org.springframework.web.bind.annotation.RestController
+
+@RestController
+@RequestMapping("/accounts/{accountUsername}/subordinates")
+class SubordinateController {
+    private val subordinateService = SubordinateService()
+
+    @GetMapping
+    fun getSubordinates(@PathVariable accountUsername: String): List<Subordinate> {
+        return subordinateService.findSubordinatesByAccount(accountUsername)
+    }
+}

modules/federation-server/src/main/kotlin/com/sphereon/oid/fed/server/federation/controllers/FederationController.kt

@@ -1,5 +1,6 @@
 package com.sphereon.oid.fed.server.federation.controllers
 
+import com.sphereon.oid.fed.services.SubordinateService
 import org.springframework.web.bind.annotation.GetMapping
 import org.springframework.web.bind.annotation.PathVariable
 import org.springframework.web.bind.annotation.RequestMapping
@@ -8,6 +9,8 @@ import org.springframework.web.bind.annotation.RestController
 @RestController
 @RequestMapping()
 class FederationController {
+    private val subordinateService = SubordinateService()
+
     @GetMapping("/.well-known/openid-federation")
     fun getRootEntityConfigurationStatement(): String {
         throw NotImplementedError()
@@ -19,8 +22,13 @@ class FederationController {
     }
 
     @GetMapping("/list")
-    fun getSubordinatesList(): List<String> {
-        throw NotImplementedError()
+    fun getRootSubordinatesList(): List<String> {
+        return subordinateService.findSubordinatesByAccountAsList("root")
+    }
+
+    @GetMapping("/{username}/list")
+    fun getSubordinatesList(@PathVariable username: String): List<String> {
+        return subordinateService.findSubordinatesByAccountAsList(username)
     }
 
     @GetMapping("/fetch")

modules/services/src/commonMain/kotlin/com/sphereon/oid/fed/services/SubordinateService.kt

@@ -0,0 +1,21 @@
+package com.sphereon.oid.fed.services
+
+import com.sphereon.oid.fed.persistence.Persistence
+import com.sphereon.oid.fed.persistence.models.Subordinate
+
+class SubordinateService {
+    private val accountRepository = Persistence.accountRepository
+    private val subordinateRepository = Persistence.subordinateRepository
+
+    fun findSubordinatesByAccount(accountUsername: String): List<Subordinate> {
+        val account = accountRepository.findByUsername(accountUsername)
+            ?: throw IllegalArgumentException(Constants.ACCOUNT_NOT_FOUND)
+
+        return subordinateRepository.findByAccountId(account.id)
+    }
+
+    fun findSubordinatesByAccountAsList(accountUsername: String): List<String> {
+        val subordinates = findSubordinatesByAccount(accountUsername)
+        return subordinates.map { it.subordinate_identifier }
+    }
+}