Core: Support pipes inside translation strings

[marcalj]

I'm submitting a ... (check one with "x")

[x] feature request

Current behavior
I'm migrating an application from AngularJS and angular-translate and I was able to use pipes inside translation strings, like:

    {
        "TEST_1": "Viewing {{ num | number:2 }} items",
        "TEST_2": "hide {{ type | translate }}",
    }

Expected/desired behavior
Be able to use pipes inside translation strings.

Reproduction of the problem
Currently you get the same translation text without parameters interpretation:

    it('should be able to get translations with nested params with pipes', () => {
        translations = {"TEST": "This is a test {{value | number}}"};
        translate.use('en');

        translate.get('TEST', {value: 12}).subscribe((res: string) => {
            expect(res).toEqual('This is a test 12');
        });
    });

Karma shows: Expected 'This is a test {{value | number}}' to equal 'This is a test 12'.

[ocombe]

I'm sorry but this is not possible in Angular because we don't have access to the compiler like we did in AngularJS...

[sebrojas14]

So? what can we do?