add dataproc_jars to templated fields in relevant dataproc operators

[mchalek]

JIRA

• My PR addresses the JIRA issue https://issues.apache.org/jira/browse/AIRFLOW-2411. It allows jar files to be specified via templates, so that we can programmatically decide which jars to use. I ran this proposed change by @fenglu-g and he agreed it was worthwhile.

Description

• Here are some details about my PR, including screenshots of any UI changes:

This is a very minor change, adding only one field (dataproc_jars) to the list of templated fields for the various DataProc operators that submit jobs requiring jar files. Note that this field is always called dataproc_jars in the operators, even though each operator's constructor has a different name for this field. So the change may look a slight bit confusing, because it might appear that the templated field should vary by operator, but this is not the case.

Tests

• My PR does not add tests because this is such a small change, and there are no tests currently in-place to test the templated fields. However we have been running Airflow at Etsy with a subset of these changes (only the change for the DataProcHadoopOperator) successfully for about a month.

Commits

• My commits all reference JIRA issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• No documentation added because none exists which specifies the templated field list for dataproc operators.

Code Quality

• Passes git diff upstream/master -u -- "*.py" | flake8 --diff

[codecov-io]

Codecov Report

Merging #3305 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3305   +/-   ##
=======================================
  Coverage   75.87%   75.87%           
=======================================
  Files         197      197           
  Lines       14710    14710           
=======================================
  Hits        11161    11161           
  Misses       3549     3549

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[Fokko]

LGTM

[mchalek]

Awesome thanks @Fokko !