feat(time_entries): add time_entries app's basic structure and endpoints

apps/time_entries/models.py

@@ -0,0 +1,81 @@
+from django.core.exceptions import ValidationError
+from django.conf import settings
+from django.db import models
+from django.db.models import Q
+
+from core.models.base import BaseModel
+from apps.workspaces.models import Workspace
+from apps.projects.models import Project
+from apps.tags.models import Tag
+
+
+User = settings.AUTH_USER_MODEL
+
+
+class TimeEntry(BaseModel):
+    workspace = models.ForeignKey(
+        Workspace,
+        on_delete=models.CASCADE,
+        related_name="time_entries",
+    )
+    user = models.ForeignKey(
+        User,
+        on_delete=models.CASCADE,
+        related_name="time_entries",
+    )
+    project = models.ForeignKey(
+        Project,
+        on_delete=models.SET_NULL,
+        null=True,
+        blank=True,
+        related_name="time_entries",
+    )
+    description = models.TextField(blank=True)
+    start_time = models.DateTimeField()
+    end_time = models.DateTimeField(null=True, blank=True)
+    duration = models.DurationField(null=True, blank=True)
+    tags = models.ManyToManyField(
+        Tag,
+        blank=True,
+        related_name="time_entries",
+    )
+    is_billable = models.BooleanField(default=False)
+    hourly_rate = models.DecimalField(
+        max_digits=10,
+        decimal_places=2,
+        null=True,
+        blank=True,
+    )
+    currency = models.CharField(
+        max_length=3,
+        default="USD",
+    )
+
+    class Meta:
+        db_table = "time_entry"
+        ordering = ("-updated_at", "-created_at")
+        indexes = [
+            models.Index(fields=["workspace"], name="time_entry_workspace_idx"),
+            models.Index(fields=["user"], name="time_entry_user_idx"),
+            models.Index(fields=["project"], name="time_entry_project_idx"),
+            models.Index(fields=["start_time"], name="time_entry_start_idx"),
+            models.Index(fields=["workspace", "start_time"], name="time_entry_workspace_start_idx"),
+        ]
+        constraints = [
+            models.UniqueConstraint(
+                fields=["workspace", "user"],
+                condition=Q(end_time__isnull=True, is_deleted=False),
+                name="unique_running_timer_per_user",
+            )
+        ]
+
+    def __str__(self):
+        return f"{self.user} - {self.start_time}"
+
+    def clean(self):
+        if self.project and self.project.workspace_id != self.workspace_id:
+            raise ValidationError("Project must belong to the same workspace.")
+
+        for tag in self.tags.all():
+            if tag.workspace_id != self.workspace_id:
+                raise ValidationError("Tags must belong to the same workspace.")