[sitecore-jss] [sitecore-jss-angular] Default Placeholder Content for empty fields in editMode metadata

[yavorsk]

• This PR follows the Contribution Guide
• Changelog updated
• Upgrade guide entry added

Description / Motivation

This PR enhances the rendering of fields in editing mode for editMode metadata. When a field value is empty, a placeholder content should be rendered to signify that the field has no value. The placeholder should be interactable, so user can add value to the field. Additionally developers can provide their own custom empty field template via the field directive's emptyFieldEditingTemplate imput property, which will be rendered instead of the default one.
The fields with this functionality are:

• [sitecore-jss-angular] image.directive.ts
• [sitecore-jss-angular] date.directive.ts
• [sitecore-jss-angular] rich-text.directive.ts
• [sitecore-jss-angular] text.directive.ts
• [sitecore-jss-angular] link.directive.ts
• [sitecore-jss-angular] router-link.directive.ts
• [sitecore-jss-angular] generic-link.directive.spec.ts

The PR also includes update to the GenericFieldValue base package type to accept Date type; this change has been made in order to make the base type compatible with the field date type defined in the angular package

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[addy-pathania]

Great work. see some comments.

[illiakovalenko]

Looks pretty good!

• please, make sure to add jsdoc comments with the right explanation where it's possible and needed
• build is failed

Also see some comments below

[illiakovalenko]

Can we just define an "input" here?

@Input('scDateEmptyFieldEditingTemplate') emptyFieldEditingTemplate: TemplateRef<unknown>;

so, we don't need to define this property on field level, since it's not used directly by field

[illiakovalenko]

Also, is it possible to initialize this input with the default value passed by the inherited class via the constructor? So we don't need to pass the default component via "renderEmpty" function

[yavorsk]

On your second comment: makes sense, Updated.
On your first comment: I tried but seems structural directives require the names of their inputs to be prefixed by the directive selector (see how the property is common but the input alias is different for each directive) - and I could not find a way around that; you can see it is done the same way for the existing inputs in link.directive and generic link directive

[illiakovalenko]

Looks good to me 👍