json2capnp: Make the cache path argument mandatory

Now that the project shortname is not an environment variable anymore
and that the project directory can be anywhere and not only in a
projects/<projectShortname> directory, it is not possible de know this
path from the .env file data. The absolute path must be set on the
command as second argument

For example, to run json2capnp for the example app, where the cache is
in `examples/runtime/demo_transition` directory, the service can be run
as `yarn start:json2capnp -- 2000
$PWD/examples/runtime/cache/demo_transition`, or `cd services/json2capnp
&& cargo run -- 2000 ../../examples/runtime/cache/demo_transition`.

The dotenv and home packages are not required anymore.

services/json2capnp/Cargo.toml

@@ -10,8 +10,6 @@ capnp = "0.14"
 rouille = "3.0"
 serde_json = "1.0"
 uuid = "0.8"
-dotenv = "0.15"
-home = "0.5"
 polyline = "0.9"
 geo = "0.17.0"
 geojson = "0.22.0"

services/json2capnp/src/main.rs

@@ -6,8 +6,6 @@
  *
  */
 
-use dotenv;
-use home;
 use rouille::Request;
 use rouille::Response;
 use std::fs;
@@ -61,15 +59,9 @@ fn main() {
 
     println!("Starting json2capnp server...");
 
-    // setup dotenv:
-    let my_env_path = home::home_dir()
-        .and_then(|a| Some(a.join("/../../../.env")))
-        .unwrap();
-    dotenv::from_path(my_env_path.as_path()).ok();
-    let project_shortname = dotenv::var("PROJECT_SHORTNAME").unwrap();
-    let project_cache_directory_path_str = cache_directory.unwrap_or(format!(
-        "../../projects/{}/cache/{}", project_shortname, project_shortname
-    ));
+    // TODO For now, the project cache directory must be set on the command line. It can come from config when config is json or yml (#415)
+    let project_shortname = "default";
+    let project_cache_directory_path_str = cache_directory.unwrap_or_else(|| { panic!("Cache directory must be set on the command line (eg cargo run -- 2000 path/to/cache/dir)") } );
     println!("Using {} as cache directory",
         project_cache_directory_path_str
     );