feat(iam): Users, orgs, policy groups

[devsjc]

Adds a first pass add hadnling IAM. It's just a first pass, and warrants some changes, but beofre I go any further, I want to commit something, as well as check that it doesn't affect benchmarks etc.

A partial address of #18.

• Have you followed the Open Climate Fix Contribution Guidelines?
• Have you referenced the Issue this PR addresses?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added a summary of the changes?
• Have you written new tests for your changes?.
• Have you successfully run make lint with your changes locally?
• Have you successfully run make gen with your changes locally?
• Have you successfully run make test with your changes locally?

[github-actions]

Benchmark Results

Benchmark results

?   	github.com/openclimatefix/data-platform/cmd	[no test files]
PASS
ok  	github.com/openclimatefix/data-platform/internal/database/dummy	0.005s
Starting TestMain
goos: linux
goarch: amd64
pkg: github.com/openclimatefix/data-platform/internal/database/postgres
cpu: AMD EPYC 7763 64-Core Processor                
BenchmarkPostgresClient/6144000/GetForecastAsTimeseries-4         	     254	   4401726 ns/op
BenchmarkPostgresClient/6144000/GetForecastAtTimestamp-4          	      61	  19307605 ns/op
BenchmarkPostgresClient/6144000/GetObservationsAsTimeseries-4     	     691	   1680034 ns/op
BenchmarkPostgresClient/6144000/CreateForecast-4                  	     482	   2413864 ns/op
PASS
Finishing TestMain
ok  	github.com/openclimatefix/data-platform/internal/database/postgres	111.774s
?   	github.com/openclimatefix/data-platform/internal/database/postgres/gen	[no test files]
?   	github.com/openclimatefix/data-platform/internal/gen/ocf/dp	[no test files]