feat: Human Input Node (#32060)

The frontend and backend implementation for the human input node.

Co-authored-by: twwu <twwu@dify.ai>
Co-authored-by: JzoNg <jzongcode@gmail.com>
Co-authored-by: yyh <92089059+lyzno1@users.noreply.github.com>
Co-authored-by: zhsama <torvalds@linux.do>

api/models/execution_extra_content.py

@@ -0,0 +1,78 @@
+from enum import StrEnum, auto
+from typing import TYPE_CHECKING
+
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from .base import Base, DefaultFieldsMixin
+from .types import EnumText, StringUUID
+
+if TYPE_CHECKING:
+    from .human_input import HumanInputForm
+
+
+class ExecutionContentType(StrEnum):
+    HUMAN_INPUT = auto()
+
+
+class ExecutionExtraContent(DefaultFieldsMixin, Base):
+    """ExecutionExtraContent stores extra contents produced during workflow / chatflow execution."""
+
+    # The `ExecutionExtraContent` uses single table inheritance to model different
+    # kinds of contents produced during message generation.
+    #
+    # See: https://docs.sqlalchemy.org/en/20/orm/inheritance.html#single-table-inheritance
+
+    __tablename__ = "execution_extra_contents"
+    __mapper_args__ = {
+        "polymorphic_abstract": True,
+        "polymorphic_on": "type",
+        "with_polymorphic": "*",
+    }
+    # type records the type of the content. It serves as the `discriminator` for the
+    # single table inheritance.
+    type: Mapped[ExecutionContentType] = mapped_column(
+        EnumText(ExecutionContentType, length=30),
+        nullable=False,
+    )
+
+    # `workflow_run_id` records the workflow execution which generates this content, correspond to
+    # `WorkflowRun.id`.
+    workflow_run_id: Mapped[str] = mapped_column(StringUUID, nullable=False, index=True)
+
+    # `message_id` records the messages generated by the execution associated with this `ExecutionExtraContent`.
+    # It references to `Message.id`.
+    #
+    # For workflow execution, this field is `None`.
+    #
+    # For chatflow execution, `message_id`` is not None, and the following condition holds:
+    #
+    # The message referenced by `message_id` has `message.workflow_run_id == execution_extra_content.workflow_run_id`
+    #
+    message_id: Mapped[str | None] = mapped_column(StringUUID, nullable=True, index=True)
+
+
+class HumanInputContent(ExecutionExtraContent):
+    """HumanInputContent is a concrete class that represents human input content.
+    It should only be initialized with the `new` class method."""
+
+    __mapper_args__ = {
+        "polymorphic_identity": ExecutionContentType.HUMAN_INPUT,
+    }
+
+    # A relation to HumanInputForm table.
+    #
+    # While the form_id column is nullable in database (due to the nature of single table inheritance),
+    # the form_id field should not be null for a given `HumanInputContent` instance.
+    form_id: Mapped[str] = mapped_column(StringUUID, nullable=True)
+
+    @classmethod
+    def new(cls, form_id: str, message_id: str | None) -> "HumanInputContent":
+        return cls(form_id=form_id, message_id=message_id)
+
+    form: Mapped["HumanInputForm"] = relationship(
+        "HumanInputForm",
+        foreign_keys=[form_id],
+        uselist=False,
+        lazy="raise",
+        primaryjoin="foreign(HumanInputContent.form_id) == HumanInputForm.id",
+    )