How to use functions in a inline HTML translate pipe?

My goal is to minimize the code using the Angular translate pipe. Currently, I have to use 8 curly brackets and write "translate" twice... a better way must exist.

My current code looks like:

<span
  *ngIf="checkoutForm.get('email')?.errors?.['email']">
  {{ 'eMail' | translate }} {{ lowerCaseFirstLetter('isInvalid' | translate) }}
</span>

And I'm trying to do shorten it in something like

<span
  *ngIf="checkoutForm.get('email')?.errors?.['email']" 
  translate>eMail {{ lowerCaseFirstLetter('isInvalid' | translate) }}
</span>

or maybe even

<span
  *ngIf="checkoutForm.get('email')?.errors?.['email']"
   translate>eMail lowerCaseFirstLetter('isInvalid')
</span>

The Text

email is a translation = E-Mail
isInvalid is a translation = Is invalid
lowerCaseFirstLetter() is a function which just lowercases first letter this is important to not destroy the orthography in other languages

You could create a custom pipe that accepts an extra parameter so you can do this:

<span
    *ngIf="checkoutForm.get('email')?.errors?.['email']"> 
    {{ 'eMail' | error:'isInvalid' }}
</span>

for that create a pipe file error.pipe.ts with following content:

import { Pipe, PipeTransform } from '@angular/core';
import { TranslateService } from '@ngx-translate/core';

@Pipe({
          name: 'error'
})

export class ErrorPipe implements PipeTransform {
          constructor(private translateService: TranslateService) {
          }
          transform(value: string, arg: string): string {
                    return `${this.translateService.instant(value)} ${this.translateService.instant(arg).toLowerCase()}`;
          }
}

declare it in the component module you want to use it in example.module.ts:

import { NgModule } from '@angular/core';  // standard
import { CommonModule } from '@angular/common';  // standard
import { ErrorPipe } from './path/to/error.pipe';

@NgModule({
  imports: [CommonModule, ExampleRoutingModule], // standard
  declarations: [ExampleComponent, ErrorPipe]
})
export class ExampleModule {}

now you can do following thing in the component:

<span
    *ngIf="checkoutForm.get('email')?.errors?.['email']"> 
    {{ 'eMail' | error:'isInvalid' }}
</span>