Add sanity checks/validations for the exporter config yaml

[Ebaneck]

Exporter crashes with the following config below:
Likely groups/label_name and the projectName in target_aws_accounts cause a duplicate label

group_by:
  enabled: true
  # Cost data can be groupped using up to two different groups: DIMENSION, TAG, COST_CATEGORY.
  # ref: https://docs.aws.amazon.com/aws-cost-management/latest/APIReference/API_GetCostAndUsageWithResources.html
  groups:
    - type: DIMENSION
      key: SERVICE
      label_name: ServiceName
    - type: TAG
      key: Project
      label_name: ProjectName

target_aws_accounts:
  - Publisher: <account-bumber>
    ProjectName: CV
    EnvironmentName: prod

2024-02-26 16:29:37,811 INFO     querying cost data for aws account <account-number>
Traceback (most recent call last):
  File "//main.py", line 72, in <module>
    main(config)
  File "//main.py", line 65, in main
    app_metrics.run_metrics_loop()
  File "/app/exporter.py", line 33, in run_metrics_loop
    self.fetch()
  File "/app/exporter.py", line 120, in fetch
    self.aws_daily_cost_usd.labels(
TypeError: prometheus_client.metrics.MetricWrapperBase.labels() got multiple values for keyword argument 'ProjectName'

[gluckzhang]

Hi @Ebaneck, thanks for reporting this issue. I see, we will add the validation asap!

[gluckzhang]

@Ebaneck feel free to give it a review #7 :)
In this PR more validations are added for the config file, including:

• label names defined in group_by should be unique
• label names defined in group_by should be different from the ones defined in target_aws_accounts

[gluckzhang]

Yesterday there was an incident in the GitHub Action that blocked the release. Now the docker image has been published and I am closing the issue :)

https://github.com/opensourceelectrolux/aws-cost-exporter/releases/tag/v1.0.3