feat: add environment variable substitution support for auth models

lib/utils/envvar_utils.dart

@@ -91,10 +91,91 @@ HttpRequestModel substituteHttpRequestModel(
       );
     }).toList(),
     body: substituteVariables(httpRequestModel.body, combinedEnvVarMap),
+    authModel:
+        _substituteAuthModel(httpRequestModel.authModel, combinedEnvVarMap),
   );
   return newRequestModel;
 }
 
+AuthModel? _substituteAuthModel(
+    AuthModel? authModel, Map<String, String> envVarMap) {
+  if (authModel == null) return null;
+
+  switch (authModel.type) {
+    case APIAuthType.basic:
+      if (authModel.basic != null) {
+        final basic = authModel.basic!;
+        return authModel.copyWith(
+          basic: basic.copyWith(
+            username: substituteVariables(basic.username, envVarMap) ??
+                basic.username,
+            password: substituteVariables(basic.password, envVarMap) ??
+                basic.password,
+          ),
+        );
+      }
+      break;
+    case APIAuthType.bearer:
+      if (authModel.bearer != null) {
+        final bearer = authModel.bearer!;
+        return authModel.copyWith(
+          bearer: bearer.copyWith(
+            token: substituteVariables(bearer.token, envVarMap) ?? bearer.token,
+          ),
+        );
+      }
+      break;
+    case APIAuthType.apiKey:
+      if (authModel.apikey != null) {
+        final apiKey = authModel.apikey!;
+        return authModel.copyWith(
+          apikey: apiKey.copyWith(
+            key: substituteVariables(apiKey.key, envVarMap) ?? apiKey.key,
+            name: substituteVariables(apiKey.name, envVarMap) ?? apiKey.name,
+          ),
+        );
+      }
+      break;
+    case APIAuthType.jwt:
+      if (authModel.jwt != null) {
+        final jwt = authModel.jwt!;
+        return authModel.copyWith(
+          jwt: jwt.copyWith(
+            secret: substituteVariables(jwt.secret, envVarMap) ?? jwt.secret,
+            privateKey: substituteVariables(jwt.privateKey, envVarMap) ??
+                jwt.privateKey,
+            payload: substituteVariables(jwt.payload, envVarMap) ?? jwt.payload,
+          ),
+        );
+      }
+      break;
+    case APIAuthType.digest:
+      if (authModel.digest != null) {
+        final digest = authModel.digest!;
+        return authModel.copyWith(
+          digest: digest.copyWith(
+            username: substituteVariables(digest.username, envVarMap) ??
+                digest.username,
+            password: substituteVariables(digest.password, envVarMap) ??
+                digest.password,
+            realm: substituteVariables(digest.realm, envVarMap) ?? digest.realm,
+            nonce: substituteVariables(digest.nonce, envVarMap) ?? digest.nonce,
+            qop: substituteVariables(digest.qop, envVarMap) ?? digest.qop,
+            opaque:
+                substituteVariables(digest.opaque, envVarMap) ?? digest.opaque,
+          ),
+        );
+      }
+      break;
+    case APIAuthType.oauth1:
+    case APIAuthType.oauth2:
+    case APIAuthType.none:
+      break;
+  }
+
+  return authModel;
+}
+
 List<EnvironmentVariableSuggestion>? getEnvironmentTriggerSuggestions(
     String query,
     Map<String, List<EnvironmentVariableModel>> envMap,