Added field descriptions and placeholders in Add API fields

[Nazarah]

Closes #3403

Changes

1. i18n.json: added templates addApi_nameFieldInfo, addApi_descriptionFieldInfo and addApi_urlFieldInfo which describe purpose of name, description and URL fields (respectively) in Add API page.

2. i18n.json: added template addApi_ownerHelpText that describes where an added API appears with what visibility.

3. schema.json: added placeholder values under autoform attribute for Name, Description and URL fields.

4. add.html: added templates texts describing the purpose of name, description and url fields.

5. add.html: added template text describing where added API appears with what visibility.

6. add.less: added new css class field-description-text to style field description texts.

Developer checklist

This checklist is to be completed by the PR developer:

• Alternative solutions were compared/discussed before writing code
  • trade-offs with this solution are considered acceptable
• Code in this PR adheres to the project styleguide
• This pull request does not decrease project test coverage
• If the code changes existing database collection(s), migration has been written
• If UI texts are added or changed, all texts are internationalized

Reviewer checklist

Reviewed by: @username1

This list is to be completed by the pull request reviewer:

• Code works as described/expected
• Code seems to be error free
  • no browser console errors visible
  • no server console errors visible
  • passes CI build
• Code is written in a way that promotes maintainability
  • easy to understand
  • well organized
  • follows project coding standards and conventions
  • well documented

[matleppa]

I'd suggest the description texts to be moved above the input field in order to keep them visible also in case the browser generates and adds a drop-down menu into input field.
An example added into issue 3403.

[55]

@matleppa let's not do it. Ecstatically it looks better as it's now. Help text != description (which has to go after title).

[Nazarah]

@matleppa before adding the templates to show help texts, the code used to be like the following:

{{# autoForm collection=ApisCollection id="addApiForm" type="insert" }}
          <!--invisible auto-value field-->
          {{> afQuickField name='latestMonitoringStatusCode' value="-1" type="hidden"}}
          <fieldset>
            {{> afQuickField name='name' id="api-name" }}
            {{> afQuickField name='description' rows=2 id="api-description" }}
            {{> afQuickField name='url' id="api-url" }}
            {{> afQuickField name='lifecycleStatus' id="api-lifecyclestatus" }}
          </fieldset>
          <button type="submit" class="btn btn-primary" id="submitapi-button">
            {{_ 'addApi_button_text' }}
          </button>
        {{/ autoForm }}

It means the fields are being populated using the Autoform package.
Also each individual field is defined using {{> afQuickField }} helpers.
For this reason, I was unable to find a way to display the help text between the input label and input field.
As an alternative solution, I added the description text for each field below the input field with by creating a new class .field-description-text in add.less

[matleppa]

@55 OK, we can call it help text instead of description.
I think that helping user has a priority over aesthetic values.

It seems that in this very case there are some challenges because of use of afQuickField.

[matleppa]

Works as expected.