feat: PC-13831 unique SLOs validation and test (#526)

## Release Notes

Added BudgetAdjustment validation for unique SLOs in filters

manifest/v1alpha/budgetadjustment/validation.go

@@ -54,7 +54,10 @@ var filtersValidationRule = validation.New(
 	validation.ForSlice(func(f Filters) []SLORef { return f.SLOs }).
 		WithName("slos").
 		Rules(validation.SliceMinLength[[]SLORef](1)).
-		IncludeForEach(sloValidationRule),
+		IncludeForEach(sloValidationRule).
+		Rules(validation.SliceUnique(func(s SLORef) string {
+			return s.Project + s.Name
+		}, "SLOs must be unique")),
 )
 
 var sloValidationRule = validation.New(

manifest/v1alpha/budgetadjustment/validation_test.go

@@ -273,6 +273,51 @@ func TestValidate_Spec(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "duplicate slo",
+			spec: Spec{
+				FirstEventStart: time.Now(),
+				Duration:        "1m",
+				Rrule:           "FREQ=WEEKLY;INTERVAL=2",
+				Filters: Filters{
+					SLOs: []SLORef{
+						{Name: "test", Project: "project"},
+						{Name: "test", Project: "project"},
+					},
+				},
+			},
+			expectedErrors: []testutils.ExpectedError{
+				{
+					Prop: "spec.filters.slos",
+					Code: validation.ErrorCodeSliceUnique,
+				},
+			},
+		},
+		{
+			name: "duplicate slo with multiple others",
+			spec: Spec{
+				FirstEventStart: time.Now(),
+				Duration:        "1m",
+				Rrule:           "FREQ=WEEKLY;INTERVAL=2",
+				Filters: Filters{
+					SLOs: []SLORef{
+						{Name: "test1", Project: "project"},
+						{Name: "test1", Project: "project"},
+						{Name: "test2", Project: "project"},
+						{Name: "test3", Project: "project"},
+						{Name: "test4", Project: "project"},
+						{Name: "test5", Project: "project"},
+						{Name: "test6", Project: "project"},
+					},
+				},
+			},
+			expectedErrors: []testutils.ExpectedError{
+				{
+					Prop: "spec.filters.slos",
+					Code: validation.ErrorCodeSliceUnique,
+				},
+			},
+		},
 		{
 			name: "proper spec",
 			spec: Spec{