Add initial support for bucket lifecycle (#7563)

This PR is based off @sinhaashish's PR for object lifecycle
management, which includes support only for,
- Expiration of object
- Filter using object prefix (_not_ object tags)

N B the code for actual expiration of objects will be included in a
subsequent PR.

pkg/lifecycle/expiration_test.go

@@ -0,0 +1,105 @@
+/*
+ * MinIO Cloud Storage, (C) 2019 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package lifecycle
+
+import (
+	"encoding/xml"
+	"fmt"
+	"testing"
+)
+
+// appropriate errors on validation
+func TestInvalidExpiration(t *testing.T) {
+	testCases := []struct {
+		inputXML    string
+		expectedErr error
+	}{
+		{ // Expiration with zero days
+			inputXML: ` <Expiration>
+                                    <Days>0</Days>
+                                    </Expiration>`,
+			expectedErr: errLifecycleInvalidDays,
+		},
+		{ // Expiration with invalid date
+			inputXML: ` <Expiration>
+                                    <Date>invalid date</Date>
+                                    </Expiration>`,
+			expectedErr: errLifecycleInvalidDate,
+		},
+		{ // Expiration with both number of days nor a date
+			inputXML: `<Expiration>
+		                    <Date>2019-04-20T00:01:00Z</Date>
+		                    </Expiration>`,
+			expectedErr: errLifecycleDateNotMidnight,
+		},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("Test %d", i+1), func(t *testing.T) {
+			var expiration Expiration
+			err := xml.Unmarshal([]byte(tc.inputXML), &expiration)
+			if err != tc.expectedErr {
+				t.Fatalf("%d: Expected %v but got %v", i+1, tc.expectedErr, err)
+			}
+		})
+
+	}
+
+	validationTestCases := []struct {
+		inputXML    string
+		expectedErr error
+	}{
+		{ // Expiration with a valid ISO 8601 date
+			inputXML: `<Expiration>
+                                    <Date>2019-04-20T00:00:00Z</Date>
+                                    </Expiration>`,
+			expectedErr: nil,
+		},
+		{ // Expiration with a valid number of days
+			inputXML: `<Expiration>
+                                    <Days>3</Days>
+                                    </Expiration>`,
+			expectedErr: nil,
+		},
+		{ // Expiration with neither number of days nor a date
+			inputXML: `<Expiration>
+                                    </Expiration>`,
+			expectedErr: errLifecycleInvalidExpiration,
+		},
+		{ // Expiration with both number of days nor a date
+			inputXML: `<Expiration>
+                                    <Days>3</Days>
+                                    <Date>2019-04-20T00:00:00Z</Date>
+                                    </Expiration>`,
+			expectedErr: errLifecycleInvalidExpiration,
+		},
+	}
+	for i, tc := range validationTestCases {
+		t.Run(fmt.Sprintf("Test %d", i+1), func(t *testing.T) {
+			var expiration Expiration
+			err := xml.Unmarshal([]byte(tc.inputXML), &expiration)
+			if err != nil {
+				t.Fatalf("%d: %v", i+1, err)
+			}
+
+			err = expiration.Validate()
+			if err != tc.expectedErr {
+				t.Fatalf("%d: %v", i+1, err)
+			}
+		})
+	}
+}