perf: reduce DB calls to GetWorkspaceByAgentID via caching workspace info (#20662)

---------

Signed-off-by: Callum Styan <callumstyan@gmail.com>

coderd/database/modelmethods.go

@@ -1,6 +1,7 @@
 package database
 
 import (
+	"database/sql"
 	"encoding/hex"
 	"slices"
 	"sort"
@@ -796,3 +797,60 @@ func (s UserSecret) RBACObject() rbac.Object {
 func (s AIBridgeInterception) RBACObject() rbac.Object {
 	return rbac.ResourceAibridgeInterception.WithOwner(s.InitiatorID.String())
 }
+
+// WorkspaceIdentity contains the minimal workspace fields needed for agent API metadata/stats reporting
+// and RBAC checks, without requiring a full database.Workspace object.
+type WorkspaceIdentity struct {
+	// Add any other fields needed for IsPrebuild() if it relies on workspace fields
+	// Identity fields
+	ID             uuid.UUID
+	OwnerID        uuid.UUID
+	OrganizationID uuid.UUID
+	TemplateID     uuid.UUID
+
+	// Display fields for logging/metrics
+	Name          string
+	OwnerUsername string
+	TemplateName  string
+
+	// Lifecycle fields needed for stats reporting
+	AutostartSchedule sql.NullString
+}
+
+func (w WorkspaceIdentity) RBACObject() rbac.Object {
+	return Workspace{
+		ID:                w.ID,
+		OwnerID:           w.OwnerID,
+		OrganizationID:    w.OrganizationID,
+		TemplateID:        w.TemplateID,
+		Name:              w.Name,
+		OwnerUsername:     w.OwnerUsername,
+		TemplateName:      w.TemplateName,
+		AutostartSchedule: w.AutostartSchedule,
+	}.RBACObject()
+}
+
+// IsPrebuild returns true if the workspace is a prebuild workspace.
+// A workspace is considered a prebuild if its owner is the prebuild system user.
+func (w WorkspaceIdentity) IsPrebuild() bool {
+	return w.OwnerID == PrebuildsSystemUserID
+}
+
+func (w WorkspaceIdentity) Equal(w2 WorkspaceIdentity) bool {
+	return w.ID == w2.ID && w.OwnerID == w2.OwnerID && w.OrganizationID == w2.OrganizationID &&
+		w.TemplateID == w2.TemplateID && w.Name == w2.Name && w.OwnerUsername == w2.OwnerUsername &&
+		w.TemplateName == w2.TemplateName && w.AutostartSchedule == w2.AutostartSchedule
+}
+
+func WorkspaceIdentityFromWorkspace(w Workspace) WorkspaceIdentity {
+	return WorkspaceIdentity{
+		ID:                w.ID,
+		OwnerID:           w.OwnerID,
+		OrganizationID:    w.OrganizationID,
+		TemplateID:        w.TemplateID,
+		Name:              w.Name,
+		OwnerUsername:     w.OwnerUsername,
+		TemplateName:      w.TemplateName,
+		AutostartSchedule: w.AutostartSchedule,
+	}
+}