Adding validatejs to validate forms

[damianpm]

What this PR does / why we need it:

Adds form validation to PF4/React forms using Validate.js

Which issue(s) this PR fixes

https://issues.jboss.org/browse/THREESCALE-2993

Special notes for your reviewer:

Pros and cons of Validate.js

Pros:

• Small (5.05KB, minified and gzipped)
• Non-intrusive (It doesn't force any styling)
• It may validate a full form or single fields
• Active project and community
• MIT License

Cons:

• Depends on jQuery (but we already have jQuery, so maybe not a con)

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Demo:

[codecov]

Codecov Report

Merging #1005 into master will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1005      +/-   ##
==========================================
- Coverage   93.03%   92.98%   -0.05%     
==========================================
  Files        2449     2447       -2     
  Lines       80830    80662     -168     
==========================================
- Hits        75197    75001     -196     
- Misses       5633     5661      +28

Impacted Files	Coverage Δ
.../initializers/backport_pg_10_support_to_rails_4.rb	30% <0%> (-50%)	⬇️
config/initializers/postgres.rb	50% <0%> (-50%)	⬇️
config/initializers/access_token_authentication.rb	55.55% <0%> (-22.23%)	⬇️
app/models/application_record.rb	62.5% <0%> (-15.63%)	⬇️
test/unit/array_test.rb	85.71% <0%> (-14.29%)	⬇️
app/queries/new_accounts_query.rb	71.73% <0%> (-10.87%)	⬇️
lib/tasks/impersonation_admin_user.rake	90% <0%> (-10%)	⬇️
app/lib/three_scale/api/responder.rb	95.74% <0%> (-2.13%)	⬇️
spec/acceptance/api/user_spec.rb
spec/acceptance/api/cms_template_spec.rb

---

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[thomasmaas]

Looks ok to me but would be good if @didierofrivia also had a look

[josemigallas]

validateAllFields is redundant, we should validate each field on change so that we can disable/enable the submit button depending on form's validity.

About the specs: they are not correct, handleChange is being mocked which is wrong (I left a comment about it). Also, there is no trace of validation in the specs although this PR is adding that. I think the following is missing:

• Add wrong value to a field -> check for "error" style and also error in state
• Add valid value to a field -> check for no "error" style and no error in state
• Add any wrong value to the form -> button should disable, and the other way around
• Check different wrong values such as empty, too short, different passwords, etc

[didierofrivia]

I've suggested just a change since I wanted to avoid duplicity since the changes suggested by @josemigallas are valid, specially the ones about the specs.

[josemigallas]

Tentatively approved