feat: create new Deployment model

[ksmuczynski]

Why

This PR addresses the following problem / context:

• Create new Deployment table to manage the many-to-many relationship between Things and Sensors.
• Allows the storage of a complete, auditable history of which specific piece of physical hardware (Sensor) was installed at which Thing and for what period of time.

How

Implementation summary - the following was changed / added / removed:

• Create Deployment model and populate with appropriate fields and relationships.

Notes

Any special considerations, workarounds, or follow-up work to note?

• This PR addresses the creation of the Deployment table only.
• Related validation schema files and test files still need to be created or updated.
• Relationships to the Deployment table still need to be defined in the core tables (Thing, Sensor).
• Transfer script needs to be created.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

Files with missing lines	Coverage Δ
db/__init__.py	97.29% <100.00%> (ø)
db/deployment.py	100.00% <100.00%> (ø)
db/sensor.py	100.00% <100.00%> (ø)
db/thing.py	100.00% <100.00%> (ø)

[jacob-a-brown]

I forgot that deployments need to be imported into db/__init__.py for their mappers to be configured and for them to be found/mapped in the DB. This can be done by adding the line

from db.deployment import *

to that file

[jacob-a-brown]

should this be named sensors since multiple sensors may be associated with a thing?