feat(functions): Allow configuration of Functions Emulator Origin

[jamesdaniels]

Checklist

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Description

Allow AngularFireFunctions to point to the Cloud Functions Emulator. This increases minimum requirement of Firebase to 5.5.7.

Code sample

Point callable Functions to the Cloud Function emulator by adding the FunctionsEmulatorOriginToken to the providers section of your NgModule.

import { NgModule } from '@angular/core';
import { AngularFireFunctionsModule, FunctionsEmulatorOriginToken } from '@angular/fire/functions';
@NgModule({
  imports: [
    ...
    AngularFireFunctionsModule,
    ...
  ],
  ...
  providers: [
   { provide: FunctionsEmulatorOriginToken, useValue: 'http://localhost:5005' }
  ]
})
export class AppModule {}

[jamesdaniels]

@davideast Ready for review. Don't merge, if approved; as I'm targeting this for the 5.2 release.

[Splaktar]

This would be nice to have! Looks like it needs a rebase tho.

[jorroll]

@jamesdaniels currently, if you are using a custom domain with firebase functions (via firebase hosting) I don't believe @angular/fire has any way of specifying the origin for callable functions requests (I believe you are forced to send callable function requests to the cloudfunctions.net domain). If a function is doing something like setting a cookie on the client, the domain used when calling the function matters.

This PR looks like it addresses that need, but, if so, the name of the token FunctionsEmulatorOriginToken is inappropriate. Might I suggest renaming it to simply FunctionsOriginToken.

[jamesdaniels]

@thefliik I like that idea, I'm also not loving the *Token pattern. Might align more with Angular here and name it FUNCTIONS_ORIGIN rather than FunctionsOriginToken

[hiepxanh]

i love this

[davideast]

LGTM