Added relationship between requirements

backend/src/models.py

@@ -193,3 +193,67 @@ class RequirementUpdateRequest(BaseModel):
     tag_id: Optional[int] = None
     priority_id: Optional[int] = None
     group_ids: Optional[List[int]] = None
+
+
+# Relationship Type schemas
+class RelationshipTypeResponse(BaseModel):
+    """Response schema for a relationship type."""
+    id: int
+    project_id: int
+    type_name: str
+    type_description: Optional[str] = None
+    inverse_type_name: Optional[str] = None
+
+    class Config:
+        from_attributes = True
+
+
+class RelationshipTypeCreateRequest(BaseModel):
+    """Request schema for creating a relationship type."""
+    type_name: str
+    type_description: Optional[str] = None
+    inverse_type_name: Optional[str] = None
+
+
+# Requirement Link schemas
+class LinkedRequirementInfo(BaseModel):
+    """Brief info about a linked requirement."""
+    id: int
+    req_name: str
+    tag_code: str
+
+    class Config:
+        from_attributes = True
+
+
+class RequirementLinkResponse(BaseModel):
+    """Response schema for a requirement link with direction."""
+    id: int
+    direction: str  # 'outgoing' or 'incoming'
+    type_name: str
+    type_id: int
+    inverse_type_name: Optional[str] = None
+    linked_requirement: LinkedRequirementInfo
+    created_by_username: Optional[str] = None
+    created_by_id: Optional[int] = None
+    created_at: Optional[datetime] = None
+
+    class Config:
+        from_attributes = True
+
+
+class RequirementLinkCreateRequest(BaseModel):
+    """Request schema for creating a requirement link."""
+    relationship_type_id: int
+    target_requirement_id: int
+
+
+# Requirement Search schemas
+class RequirementSearchResult(BaseModel):
+    """Response schema for requirement search results (for autocomplete)."""
+    id: int
+    req_name: str
+    tag_code: str
+
+    class Config:
+        from_attributes = True