added option to specify profile when connecting to redshift via IAM

[brunomurino]

resolves #2437

Description

Added option to specify profile when connecting to redshift via IAM

Checklist

• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

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[jtcohen6]

@brunomurino The errors from flake8 have to do with pep8 style. I pulled this out of the CircleCI logs:

flake8 run-test: commands[0] | /bin/bash -c '$(which flake8) --select=E,W,F --ignore=W504,E741 core/dbt plugins/*/dbt'
plugins/redshift/dbt/adapters/redshift/connections.py:60:80: E501 line too long (85 > 79 characters)
plugins/redshift/dbt/adapters/redshift/connections.py:90:80: E501 line too long (81 > 79 characters)
plugins/redshift/dbt/adapters/redshift/connections.py:98:80: E501 line too long (90 > 79 characters)
ERROR: InvocationError for command /bin/bash -c '$(which flake8) --select=E,W,F --ignore=W504,E741 core/dbt plugins/*/dbt' (exited with code 1)

If you run make test-unit locally, it should include flake8 testing as well.

[drewbanin]

One quick comment here, but overall, this looks great!

[drewbanin]

I think we may not want to hard-code this region name here. Do you think this should be an option in the profile? Or even better, can we document that the region should be specified in the configured AWS IAM profile?

[brunomurino]

Ops, my bad, I didn't mean to add that, just pushed the fix. Yea, I think everything should be specified in the profile.

Is there a repo for the user documentation? Couldn't find anything in the dbt repo

[beckjake]

The documentation is maintained in this repository: https://github.com/fishtown-analytics/docs.getdbt.com/

[beckjake]

I have some changelog-formatting feedback, but the code looks good to me!

[beckjake]

Instead of adding this ### Next section at the top, can you add a ### Features section under the ## dbt 0.18.0 (Release TBD) line, and add your line there? Please also add a link to the issue/PR, like the other features listed!

Also, please add a new contributors section to the ## dbt 0.18.0 (Release TBD) section with your username and a link here. Check out lower down in the file for the exact formatting!

[brunomurino]

Done!

[beckjake]

Two tiny suggestions on the changelog formatting, this looks good to me.

[brunomurino]

I think the test failed for an unrelated issue. Can someone rerun the tests?

[brunomurino]

Is it all good with this now?

[jtcohen6]

This looks great, @brunomurino. Thank you for the contribution!