Remove default feature from Cargo.toml

In the prev commit, we don't use default features in dependencies by default.
But it's not clear for rust-analyzer or other toolchains which are not
integrated to our build system.

To make it simplify, this change removes all `default` feature set from
Cargo.toml in this repository.

This express that this project requires an additional way to enable
toolchain supports which is not added to our build system.

Drawbacks
--------

1. rust-analyzer does not support editor agnostic setting.
   A developer that do not use vscode would requires additional config.
   rust-lang/rust-analyzer#11010
2. This requires to commit `.vscode/settings.json`.

.vscode/settings.json

@@ -0,0 +1,8 @@
+{
+    "rust-analyzer.cargo.features": [
+        // We want to be able to rollout this application to production at all
+        // Thus we use _production_ as our default build feature set.
+        "c_at_e_main/production"
+    ],
+    "rust-analyzer.cargo.noDefaultFeatures": true,
+}

Makefile

@@ -53,6 +53,9 @@ FASTLY_TOML_ENV ?= ""
 ###########################
 # Release Channel Mechanism
 ###########################
+
+# We want to be able to rollout this application to production at all time.
+# Thus we use _production_ as our default build feature set.
 RELEASE_CHANNEL ?= production
 
 RELEASE_CHANNEL_FEATURES :=

crates/main/Cargo.toml

@@ -9,13 +9,6 @@ rust-version.workspace = true
 fastly = "^0.8.7"
 
 [features]
-# Our build system requires to set _release channel_ explicitly by using `--no-default-features`.
-# This default set is only used for toolchains that are not integrated our build systems (e.g. rust-analyzer).
-default = [
-    # We want to be able to rollout this application to production at all time.
-    # Thus we use _production_ as our default build feature set.
-    "production"
-]
 
 # These feature flags represents _release channel_.
 # These are mutually exclusive. You cannot enable both of them.