feat: add reusable solution library

backend/apps/solutions/models.py

@@ -0,0 +1,64 @@
+from django.conf import settings
+from django.db import models
+
+from apps.tickets.models import Ticket, TicketCategory
+
+
+class Solution(models.Model):
+    title = models.CharField(max_length=200)
+    problem_signature = models.TextField()
+    related_system = models.CharField(max_length=120, blank=True)
+    environment_scope = models.CharField(max_length=120, blank=True)
+    category = models.ForeignKey(TicketCategory, null=True, blank=True, on_delete=models.SET_NULL)
+    root_cause = models.TextField()
+    solution = models.TextField()
+    risk_note = models.TextField(blank=True)
+    status = models.CharField(max_length=40, default="draft")
+    usage_count = models.PositiveIntegerField(default=0)
+    created_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+    class Meta:
+        ordering = ["-updated_at"]
+
+    def __str__(self) -> str:
+        return self.title
+
+
+class TicketResolution(models.Model):
+    ticket = models.OneToOneField(Ticket, on_delete=models.CASCADE, related_name="resolution")
+    resolution_type = models.CharField(max_length=80, default="resolved")
+    root_cause = models.TextField(blank=True)
+    solution_text = models.TextField()
+    linked_solution = models.ForeignKey(Solution, null=True, blank=True, on_delete=models.SET_NULL)
+    confirmed_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+    updated_at = models.DateTimeField(auto_now=True)
+
+
+class TicketSolutionLink(models.Model):
+    ticket = models.ForeignKey(Ticket, on_delete=models.CASCADE, related_name="solution_links")
+    solution = models.ForeignKey(Solution, on_delete=models.CASCADE, related_name="ticket_links")
+    link_type = models.CharField(max_length=40, default="referenced")
+    agent_run_id = models.BigIntegerField(null=True, blank=True)
+    created_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+    )
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        unique_together = [("ticket", "solution", "link_type")]