Add feature to support auto-migration for both ArangoDB and ElasticSearch

[sigma1326]

The current database schema does not support auto-migration. When the codebase gets larger, it will be much harder to update both databases according to the new changes. It is better to have a mechanism to automatically detect changes in the schema and add necessary updates if possible. Only changes that cannot be solved using the auto-migration tool should be shown to the user. Moreover, this mechanism should check whether the new schema can be updated without any error.