Feature/acs 2147 add get storage object props in content store (#769)

* ACS-2147: initial idea for adding storage properties to ContentStore.

* ACS-2147: adding implementations to ContentStore children + some static analysis cleanup.

* ACS-2147: adding javadoc and small fixes to ObjectStorageProps.

* License header update

Co-authored-by: David Edwards <david.edwards@alfresco.com>

* License header update

Co-authored-by: David Edwards <david.edwards@alfresco.com>

* ACS-2147: initial idea for adding storage properties to ContentStore.

* ACS-2147: adding implementations to ContentStore children + some static analysis cleanup.

* ACS-2147: adding javadoc and small fixes to ObjectStorageProps.

* License header update

Co-authored-by: David Edwards <david.edwards@alfresco.com>

* License header update

Co-authored-by: David Edwards <david.edwards@alfresco.com>

* ACS-2147: Adding unit tests and changes after first round of code review.

* ACS-2147: initial idea for adding storage properties to ContentStore.

* ACS-2147: adding implementations to ContentStore children + some static analysis cleanup.

* ACS-2147: adding javadoc and small fixes to ObjectStorageProps.

* License header update

Co-authored-by: David Edwards <david.edwards@alfresco.com>

* License header update

Co-authored-by: David Edwards <david.edwards@alfresco.com>

* ACS-2147: Adding unit tests and changes after first round of code review.

* ACS-2147: adding implementations to ContentStore children + some static analysis cleanup.

* License header update

Co-authored-by: David Edwards <david.edwards@alfresco.com>

* ACS-2147: Fixes after reverting some 'boy scout' refactor.

* ACS-2147: Rephrasing Alfresco-derived storage properties.

* ACS-2147: Reverting some 'boy scout' refactor.

* ACS-2147: Renaming enum values.

* ACS-2147: Removing wildcard import.

Co-authored-by: David Edwards <david.edwards@alfresco.com>

data-model/src/main/java/org/alfresco/repo/content/ContentStore.java

@@ -26,6 +26,7 @@
 package org.alfresco.repo.content;
 
 import org.alfresco.api.AlfrescoPublicApi;
+import org.alfresco.service.Experimental;
 import org.alfresco.service.cmr.repository.ContentAccessor;
 import org.alfresco.service.cmr.repository.ContentIOException;
 import org.alfresco.service.cmr.repository.ContentReader;
@@ -33,6 +34,9 @@ import org.alfresco.service.cmr.repository.ContentStreamListener;
 import org.alfresco.service.cmr.repository.ContentWriter;
 import org.alfresco.service.cmr.repository.DirectAccessUrl;
 
+import java.util.Collections;
+import java.util.Map;
+
 
 /**
  * Provides low-level retrieval of content
@@ -324,4 +328,20 @@ public interface ContentStore
         throw new UnsupportedOperationException(
                 "Retrieving direct access URLs is not supported by this content store.");
     }
+
+    /**
+     * Gets a key-value (String-String) collection of storage headers/properties with their respective values.
+     * A particular Cloud Connector will fill in that data with Cloud Storage Provider generic data.
+     * Map may be also filled in with entries consisting of pre-defined Alfresco keys of {@code ObjectStorageProps} and their values.
+     * If empty Map is returned - no connector is present or connector is not supporting retrieval of the properties
+     * or cannot determine the properties.
+     *
+     * @param contentUrl the URL of the content for which the storage properties are to be retrieved.
+     * @return Returns a key-value (String-String) collection of storage headers/properties with their respective values.
+     */
+    @Experimental
+    default Map<String, String> getObjectStorageProperties(String contentUrl)
+    {
+        return Collections.emptyMap();
+    }
 }

data-model/src/main/java/org/alfresco/repo/content/ObjectStorageProps.java

@@ -0,0 +1,64 @@
+/*
+ * #%L
+ * Alfresco Data model classes
+ * %%
+ * Copyright (C) 2005 - 2021 Alfresco Software Limited
+ * %%
+ * This file is part of the Alfresco software.
+ * If the software was purchased under a paid Alfresco license, the terms of
+ * the paid license agreement will prevail.  Otherwise, the software is
+ * provided under the following open source license terms:
+ *
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ * #L%
+ */
+
+package org.alfresco.repo.content;
+
+import org.alfresco.service.Experimental;
+
+/**
+ * Enumeration with "header" values for Alfresco derived Storage Properties
+ * Values of this enum should be used when adding Alfresco derived key-value pairs in Storage Properties map.
+ * Subject to expand/change.
+ *
+ * @author mpichura
+ */
+@Experimental
+public enum ObjectStorageProps {
+    /**
+     * Object's content is archived and not immediately accessible.
+     */
+    X_ALF_ARCHIVED("x-alf-archived"),
+    /**
+     * Object's content retrieval from archive is in progress
+     */
+    X_ALF_ARCHIVE_RESTORE_IN_PROGRESS("x-alf-archive-restore-in-progress"),
+    /**
+     * Expiry date and time of object's content retrieved from archive.
+     * Use YYYYMMDDThhmmssZ (ISO-8601) datetime format when using this value as key in Storage Properties map.
+     */
+    X_ALF_ARCHIVE_RESTORE_EXPIRY("x-alf-archive-restore-expiry");
+
+    ObjectStorageProps(String value) {
+        this.value = value;
+    }
+
+    private final String value;
+
+    public String getValue() {
+        return value;
+    }
+
+}