[FEATURE] new @Env('Project specific configs') which should fetch by autocompletion all env files of the project

[dragolea]

Description

Currently there's not specific decorator to fetch ENV variables + the typing of cds.env is not finished entirely

Currently the cds.env looks like below

/**
 * Access to the configuration for Node.js runtime and tools.
 * The object is the effective result of configuration merged from various sources,
 * filtered through the currently active profiles, thus highly dependent on the current working
 * directory and process environment.
 */
export const env: {
    build: _TODO,
    hana: _TODO,
    i18n: {
        languages: string[],
        default_language: string,
        folders: string[],
        [key: string]: any,
    },
    profiles: string[],
    requires: env.Requires,
    folders: {
        app: string,
        db: string,
        srv: string,
        fts: string,
        [key: string]: string, // to allow additional values
    },
    odata: _TODO,
    query: _TODO,
    sql: _TODO,
} & { [key: string]: any };

Suggested solution

A @Env decorator and getting autocompletion of all env files as properties would be useful.