Feat/environment variables in workflow (#6515)

Co-authored-by: JzoNg <jzongcode@gmail.com>

api/core/app/segments/segments.py

@@ -0,0 +1,39 @@
+from typing import Any
+
+from pydantic import BaseModel, ConfigDict, field_validator
+
+from .types import SegmentType
+
+
+class Segment(BaseModel):
+    model_config = ConfigDict(frozen=True)
+
+    value_type: SegmentType
+    value: Any
+
+    @field_validator('value_type')
+    def validate_value_type(cls, value):
+        """
+        This validator checks if the provided value is equal to the default value of the 'value_type' field.
+        If the value is different, a ValueError is raised.
+        """
+        if value != cls.model_fields['value_type'].default:
+            raise ValueError("Cannot modify 'value_type'")
+        return value
+
+    @property
+    def text(self) -> str:
+        return str(self.value)
+
+    @property
+    def log(self) -> str:
+        return str(self.value)
+
+    @property
+    def markdown(self) -> str:
+        return str(self.value)
+
+
+class StringSegment(Segment):
+    value_type: SegmentType = SegmentType.STRING
+    value: str