Add warnings to the system

## Background
There can be some discrepancies in the source files.

## Feature
Raise warnings when a discrepancy is detected.

## Warnings to check
(Not exhaustive)
1. Function schema differs from directory
2. Function name differs from file name
3. Table name differs from file name
4. Missing schema owner
5. No function owner
6. No table owner
7. Table column drop
8. Table drop
9. Unrecognized files in the sources