Backend/feature/symmetric conflict

[VentusXu09]

Title

Add resolution for symmetricDS conflict

Description

182

The symmetricDS will choose the latest updated data to insert/update when conflicts happen. Add create/update timestamp column into agsensor, agsensortype, agvenue and agevent. The create/update timestamp will be created/updated by django automatically.

Types of Changes

Put an x in the boxes that apply

• [ ] Feature (non-breaking change which adds functionality)
• [x] Bug Fix (non-breaking change that fixes an issue)
• [ ] Breaking Change (feature/fix that causes existing features to not work as expected)
• [ ] Documentation

Checklist

• [ ] I have read the [contribute]contributing doc
• [ ] Classes, scripts, and environment variables follow existing naming convention
• [x] Lint and Unit tests pass locally
• [ ] New features on hardware have been tested on a local Raspberry Pi
• [ ] Mention new programs/binaries if any must be installed along with this change
• [ ] Mention new environment variables if any have been added to hardware/env file
• [x] Test coverage should not drop more than 3%
• [ ] Any new required python modules are added to the requirements.txt

[VentusXu09]

Get pain on models.DateTimeField(auto_now=True). Please see this discussion for more details.

Waiting for #181 solved to try USE_PK as detect_type.