feat: add trial model list in system features (#31313)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: hj24 <mambahj24@gmail.com>

api/enums/hosted_provider.py

@@ -0,0 +1,21 @@
+from enum import StrEnum
+
+
+class HostedTrialProvider(StrEnum):
+    """
+    Enum representing hosted model provider names for trial access.
+    """
+
+    OPENAI = "langgenius/openai/openai"
+    ANTHROPIC = "langgenius/anthropic/anthropic"
+    GEMINI = "langgenius/gemini/google"
+    X = "langgenius/x/x"
+    DEEPSEEK = "langgenius/deepseek/deepseek"
+    TONGYI = "langgenius/tongyi/tongyi"
+
+    @property
+    def config_key(self) -> str:
+        """Return the config key used in dify_config (e.g., HOSTED_{config_key}_PAID_ENABLED)."""
+        if self == HostedTrialProvider.X:
+            return "XAI"
+        return self.name