angular-l10n pluralization with ICU messageformat

Question

We are testing with the angular-l10n package to implement localization in our angular 7 project. We have run into some challenges with plural translations. We are trying to port over some Spanish translations being used in our angular JS implementation as follows:

"unit":       "{{count, plural, =1 {unidad} other {unidades} }}"

This is consistent with the ICU messageformat here - http://userguide.icu-project.org/formatparse/messages"

However, this format is not supported by the i18nPluralPipe's pluralMap variable. I am able to implement using a pluralMap variable as follows:

itemPluralMapping = {
    'unit': {
        '=0': 'unit', '=1': 'unit', 'other': 'units'

    }
}

With the template as follows:

<p>{{units | i18nPlural:itemPluralMapping['unit'] | translate:lang}}</p>

I am even able to put it directly in the template as follows:

<span i18n>{count, plural, =1 {{{'unit' | translate:lang }}} other {{{'units' | translate:lang }}}}</span>

However, how can the following entry in the locale-es.json work?

"unit":       "{{count, plural, =1 {unidad} other {unidades} }}"