Add support to multi-account environments

[lakkeger]

Motivation

tflocal is only usable currently with a single account as all resources are deployed into the default one. This behavior is not ideal to run tests or develop code for many production cases when terraform code references to resources outside of this account ie to manage a domain registration or validate certificates on a central DNS managing account.

Related issue: #29

Changes

• Added new env variable to trigger look up for provided possible override values instead of the mocked access key
• Added tests regarding above functionality

TODO

• [x] Trigger predefined access key usage for CUSTOMISE_ACCESS_KEY=1
• [x] Use AWS_ACCESS_KEY_ID environment variable
• [x] Use boto3 to get ACCESS_KEY_ID from default session
• [x] Use AWS_PROFILE or AWS_DEFAULT_PROFILE variable to get access key
• [x] Use access key from Terraform files
• [x] ~Import original arguments into the mock file~
• [x] Test above use cases and edge cases
• [x] Sync region and access key behavior

[cshimmin]

As an interested observer from the US, I recommend either supporting the alternative spelling CUSTOMIZE_ACCESS_KEY, or avoid the ambiguity altogether with a different name. Perhaps ACCESS_KEY_PASSTHROUGH?

[alexrashed]

Hi @cshimmin!

As an interested observer from the US, I recommend either supporting the alternative spelling CUSTOMIZE_ACCESS_KEY, or avoid the ambiguity altogether with a different name. Perhaps ACCESS_KEY_PASSTHROUGH?

Thanks for the comment! Actually, that was one of @whummer's PR review comments and @lakkeger already changed it in the code (but not yet in the PR description). 😛