[OGUI-1459] Refactor Lock API to allow for future easy improvements addition

[graduta]

I have JIRA issue created

• branch and/or PR name(s) includes JIRA ID
• issue has "Fix version" assigned
• issue "Status" is set to "In review"
• PR labels are selected
• FLP integration tests were ran successful

PR which:

• update API routes to follow convention on both front-end and back-end
• adds controller for lock requests
• adds service for lock operations
• adds DTOs for Lock and User plus conversions for JSON for private attributes)
• updates and complements back-end tests accordingly

Future improvements are needed as:

• using cache service for keeping track of locks
• allowing one request per lock operation
• allowing the take/release of multiple locks at the same time