docs: Example showing how to use default settings for workflow spec. Related to ##2388

[NikeNano]

This PR includes an example on how to use the default workflow specs in order to allow users set default specs for workflows. The defaults will only be used if the spec is not set.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this is a chore.
• The title of the PR is (a) conventional, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234".
• I have written unit and/or e2e tests for my change. PRs without these are unlike to be merged.
• Optional. I've added My organization is added to the USERS.md.
• I've signed the CLA and required builds are green.

[NikeNano]

@JohanWork would you like to check this out?

[codecov]

Codecov Report

Merging #2411 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2411   +/-   ##
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  Coverage   13.13%   13.13%           
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  Files          72       72           
  Lines       25084    25084           
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  Hits         3294     3294           
  Misses      21375    21375           
  Partials      415      415

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[alexec]

Looks good! Some comments.

[alexec]

There is an example config map in the docs folder. Could you put your example here please?

[NikeNano]

I am not sure if I understand exactly what you want me to add so please give feedback on the changes of the example of the config map.

[alexec]

I think you example is fine, but should be in docs/workflow-controller-configmap.yaml

[NikeNano]

There seams to be some issues in terms of how the value get set. I did some extra tests and the following is the updated wf:

Kind:         Workflow
Metadata:
  Creation Timestamp:             2020-03-12T06:47:10Z
  Deletion Grace Period Seconds:  0
  Deletion Timestamp:             2020-03-12T06:47:28Z
  Finalizers:
    foregroundDeletion
  Generate Name:     coinflip-
  Generation:        10
  Resource Version:  32192
  Self Link:         /apis/argoproj.io/v1alpha1/namespaces/argo/workflows/coinflip-5d4cs
  UID:               01a3e395-92d5-41dd-93db-83ccd3c7be61
Spec:
  Arguments:
  Entrypoint:  coinflip
  Templates:
    Inputs:
    Metadata:
    Name:  coinflip
    Outputs:
    Steps:
      [map[arguments:map[] name:flip-coin template:flip-coin]]
      [map[arguments:map[] name:heads template:heads when:{{steps.flip-coin.outputs.result}} == heads] map[arguments:map[] name:tails template:tails when:{{steps.flip-coin.outputs.result}} == tails]]
    Inputs:
    Metadata:
    Name:  flip-coin
    Outputs:
    Script:
      Command:
        python
      Image:  python:alpine3.6
      Name:   
      Resources:
      Source:  import random
result = "heads" if random.randint(0,1) == 0 else "tails"
print(result)

    Container:
      Args:
        echo "it was heads"
      Command:
        sh
        -c
      Image:  alpine:3.6
      Name:   
      Resources:
    Inputs:
    Metadata:
    Name:  heads
    Outputs:
    Container:
      Args:
        echo "it was tails"
      Command:
        sh
        -c
      Image:  alpine:3.6
      Name:   
      Resources:
    Inputs:
    Metadata:
    Name:  tails
    Outputs:
  Ttl Strategy:
    Seconds After Completion:  10

I don't get why there is spacing in "Ttl Strategy: " and "Seconds After Completion: 10". Is this an issue @alexec

[alexec]

Great stuff -- thank you!!