feat: disable HTTP API by default, make it opt-in

BREAKING CHANGE: HTTP API is now disabled by default and must be explicitly
enabled in configuration.

Changes:
- Move HTTP config from :api_port and :api_ip to nested :http config
- Add :http :enabled flag (defaults to false)
- Conditionally start Web.Supervisor only when HTTP is enabled
- Update all environment configs:
  - config.exs: HTTP disabled by default
  - dev.exs: HTTP enabled for development
  - test.exs: HTTP disabled for unit tests
  - e2e_test.exs: HTTP enabled for e2e tests
  - prod.exs: HTTP enabled by default, configurable via CONCORD_HTTP_ENABLED

To enable HTTP API in production:
- Set CONCORD_HTTP_ENABLED=true environment variable
- Or configure in config/runtime.exs:
  config :concord, :http, enabled: true

This change allows Concord to be used as an embedded library without
the HTTP API overhead when not needed.

Author: GSMLG-BOT

config/config.exs

@@ -27,9 +27,14 @@ config :concord,
     level: 6
   ],
   # HTTP API configuration
-  api_port: 4000,
-  # localhost
-  api_ip: {127, 0, 0, 1},
+  http: [
+    # Enable HTTP/HTTPS API server (disabled by default)
+    enabled: false,
+    # API server port
+    port: 4000,
+    # API server IP (localhost by default)
+    ip: {127, 0, 0, 1}
+  ],
   # TLS/HTTPS configuration
   tls: [
     # Enable HTTPS instead of HTTP

config/dev.exs

@@ -2,6 +2,11 @@ import Config
 
 config :concord,
   data_dir: "./data/dev",
-  auth_enabled: false
+  auth_enabled: false,
+  http: [
+    enabled: true,
+    port: 4000,
+    ip: {127, 0, 0, 1}
+  ]
 
 config :logger, level: :debug

config/e2e_test.exs

@@ -17,9 +17,7 @@ config :libcluster,
 config :logger, level: :warning
 
 # HTTP API configuration for e2e tests
-config :concord, :http,
-  enabled: true,
-  port: 4000
+config :concord, :http, enabled: true, port: 4000
 
 # Telemetry configuration
 config :concord, :telemetry, enabled: true

config/prod.exs

@@ -4,7 +4,10 @@ config :concord,
   data_dir: {:system, "CONCORD_DATA_DIR", "/var/lib/concord"},
   auth_enabled: true,
   # Production HTTP API configuration
-  api_port: {:system, "CONCORD_API_PORT", 8080},
-  api_ip: {:system, "CONCORD_API_IP", {0, 0, 0, 0}}
+  http: [
+    enabled: {:system, "CONCORD_HTTP_ENABLED", true},
+    port: {:system, "CONCORD_API_PORT", 8080},
+    ip: {:system, "CONCORD_API_IP", {0, 0, 0, 0}}
+  ]
 
 config :logger, level: :info

config/test.exs

@@ -2,6 +2,7 @@ import Config
 
 config :concord,
   data_dir: "./data/test",
-  auth_enabled: false
+  auth_enabled: false,
+  http: [enabled: false]
 
 config :logger, level: :warning

lib/concord/application.ex

@@ -60,12 +60,19 @@ defmodule Concord.Application do
       {TTL, []},
       # Start multi-tenancy rate limiter
       MultiTenancy.RateLimiter,
-      # Start HTTP API web server
-      Web.Supervisor,
       # Start the Concord cluster after a brief delay
       {Task, fn -> init_cluster() end}
     ]
 
+    # Add HTTP API web server if enabled
+    children =
+      if http_api_enabled?() do
+        # Insert Web.Supervisor before the cluster init task
+        List.insert_at(children, -1, Web.Supervisor)
+      else
+        children
+      end
+
     # Add Prometheus exporter if enabled
     children =
       if prometheus_enabled?() do
@@ -94,6 +101,11 @@ defmodule Concord.Application do
     Supervisor.start_link(children, opts)
   end
 
+  defp http_api_enabled? do
+    Application.get_env(:concord, :http, [])
+    |> Keyword.get(:enabled, false)
+  end
+
   defp prometheus_enabled? do
     Application.get_env(:concord, :prometheus_enabled, true)
   end

lib/concord/web/supervisor.ex

@@ -40,7 +40,8 @@ defmodule Concord.Web.Supervisor do
   defp get_port do
     case System.get_env("CONCORD_API_PORT") do
       nil ->
-        Application.get_env(:concord, :api_port, 4000)
+        http_config = Application.get_env(:concord, :http, [])
+        Keyword.get(http_config, :port, 4000)
 
       port_str ->
         case Integer.parse(port_str) do
@@ -53,7 +54,10 @@ defmodule Concord.Web.Supervisor do
   defp get_ip do
     case System.get_env("CONCORD_API_IP") do
       nil ->
-        case Application.get_env(:concord, :api_ip, {127, 0, 0, 1}) do
+        http_config = Application.get_env(:concord, :http, [])
+        default_ip = Keyword.get(http_config, :ip, {127, 0, 0, 1})
+
+        case default_ip do
           {a, b, c, d} = ip when a in 0..255 and b in 0..255 and c in 0..255 and d in 0..255 -> ip
           :loopback -> {127, 0, 0, 1}
           :any -> {0, 0, 0, 0}