hook up showing survey prompt if not taken or recently prompted

[tejal29]

Fixes: #4046

In this PR, skaffold will show the survey prompt to users if

1. The survey was not taken in last 3 months and
2. The survey prompt was not show in last 2 weeks.

** UI Changes **

** Testing**

1. Unit tests here cover all the below tests.

** Manual tests **

1. Survey not taken in last 3 months or not prompted recently
a. ~/.skaffold/config :

(add_survey_check)cat ~/.skaffold/config 
global:
  survey: {}
kubeContexts: []
 (add_survey_check)

b. Run any skaffold command

../../out/skaffold run -d gcr.io/tejal-test
Generating tags...
...
You can also run [skaffold run --tail] to get the logs
Help improve Skaffold! Take a 10-second anonymous survey by running
   skaffold survey
(add_survey_check)

2. Survey not taken in last 3 months but prompted recently
a. Skaffold config

(add_survey_check)cat ~/.skaffold/config 
global:
  survey:
    last-prompted: "2020-06-09T10:34:05-07:00"
kubeContexts: []

b. Run skaffold command and verify prompt is not shown.

(add_survey_check)../../out/skaffold run -d gcr.io/tejal-test
Generating tags...
....
You can also run [skaffold run --tail] to get the logs
 (add_survey_check)

3. Survey not taken in last 3 months but prompted but 2 weeks ago
a. set survey prompted taken to last month

(add_survey_check)skaffold config set --survey --global last-prompted "2020-05-15T10:34:05-07:00"
set global value last-prompted to 2020-05-15T10:34:05-07:00

b. Run any skaffold command and verify the prompt is shown.

(add_survey_check)./../out/skaffold run -d gcr.io/tejal-test
Generating tags...
....
You can also run [skaffold run --tail] to get the logs
Help improve Skaffold! Take a 10-second anonymous survey by running
   skaffold survey

4. Survey taken in last 3 months.
a. Set survey taken in last 3 months and not recently prompted

skaffold config set --survey --global last-taken "2020-04-30T10:34:05-07:00"
set global value last-taken to 2020-04-30T10:34:05-07:00

skaffold config unset --survey --global last-prompted
unset global value last-prompted

cat ~/.skaffold/config 
global:
  survey:
    last-taken: "2020-04-30T10:34:05-07:00"
kubeContexts: []
tejaldesai@tejaldesai-macbookpro2 getting-started (add_survey_check)

b. Run skaffold command and verify the prompt is not displayed

(add_survey_check)../../out/skaffold run -d gcr.io/tejal-test
Generating tags...
 ...
Deployments stabilized in 132.179878ms
You can also run [skaffold run --tail] to get the logs
tejaldesai@tejaldesai-macbookpro2 getting-started (add_survey_check)

[codecov]

Codecov Report

Merging #4306 into master will decrease coverage by 0.01%.
The diff coverage is 59.37%.

@@            Coverage Diff             @@
##           master    #4306      +/-   ##
==========================================
- Coverage   71.93%   71.91%   -0.02%     
==========================================
  Files         322      322              
  Lines       12313    12341      +28     
==========================================
+ Hits         8857     8875      +18     
- Misses       2896     2902       +6     
- Partials      560      564       +4     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/cmd.go	67.64% <30.00%> (-1.89%)	⬇️
pkg/skaffold/config/util.go	71.26% <70.00%> (-0.35%)	⬇️
pkg/skaffold/survey/survey.go	52.94% <100.00%> (+21.69%)	⬆️
...affold/kubernetes/portforward/kubectl_forwarder.go	60.97% <0.00%> (-2.44%)	⬇️

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[nkubala]

a few wording suggestions and one comment but in general LGTM

[nkubala]

is this something we actually want the user to do? feels a little weird that we'd tell them to run a command to set a prompt timestamp - maybe we should tell them if this keeps happening to disable instead?

[tejal29]

if we ask users to disable the prompt, they would never see the prompt.
This command would silence it for 2 weeks.

How about we add the command to disable permanently here -> https://skaffold.dev/docs/resources/feedback/ or as part of FAQ.
And change the message to

could not automatically update the survey prompted timestamp - 
please run skaffold config set --survey --global last-prompted 2019-10-20XXX 
or see <> to permanently disable the prompt. 

Or

could not automatically update the survey prompted timestamp
 - please run 
skaffold config set --survey --global last-prompted 2019-10-20XXX 
 or  
run `skaffold config set --survey --global disable-prompt true` to permanently disable the prompt.

[nkubala]

in any case we're still asking the user to run a command...but after thinking about it a little more I think it's probably fine. we can always change it later if it seems too annoying