AutoEntityService: Support supplying a function to host in config.

[colesanders]

AutoEntityService

Feature Request:

When providing the host to the AutoEntityServiceModule config, currently only a string can be passed. Allowing a function to be provided would allow the host to be fetched dynamically at runtime instead of bootstrap. This would be helpful for hybrid apps and other use cases where the api endpoint might be dependent on the request or platform.

NgrxAutoEntityServiceModule.forRoot({
  host: ((entityInfo: IEntityInfo, operation: string, criteria: EntityCriteria) => string) | string;
})