feat: add BLOCKSCOUT_HOST, and use it in API docs

CHANGELOG.md

@@ -5,6 +5,7 @@
 - [#2075](https://github.com/poanetwork/blockscout/pull/2075) - add blocks cache
 - [#2151](https://github.com/poanetwork/blockscout/pull/2151) - hide dropdown menu then other networks list is empty
 - [#2146](https://github.com/poanetwork/blockscout/pull/2146) - feat: add eth_getLogs rpc endpoint
+- [#2193](https://github.com/poanetwork/blockscout/pull/2193) - feat: add BLOCKSCOUT_HOST, and use it in API docs
 
 ### Fixes
 - [#2201](https://github.com/poanetwork/blockscout/pull/2201) - footer columns fix

apps/block_scout_web/config/config.exs

@@ -41,7 +41,7 @@ config :block_scout_web, BlockScoutWeb.Endpoint,
     ]
   ],
   url: [
-    host: "localhost",
+    host: System.get_env("BLOCKSCOUT_HOST") || "localhost",
     path: System.get_env("NETWORK_PATH") || "/"
   ],
   render_errors: [view: BlockScoutWeb.ErrorView, accepts: ~w(html json)],

apps/block_scout_web/lib/block_scout_web/templates/api_docs/eth_rpc.html.eex

@@ -2,7 +2,7 @@
   <div class="card">
     <div class="card-body">
       <h1 class="card-title margin-bottom-sm"><%= gettext("ETH RPC API Documentation") %></h2>
-      <p class="api-text-monospace" data-endpoint-url="<%= BlockScoutWeb.Endpoint.url() %>/api/eth_rpc">[ <%= gettext "Base URL:" %> <%= @conn.host %>/api/eth_rpc ]</p>
+      <p class="api-text-monospace" data-endpoint-url="<%= BlockScoutWeb.Endpoint.url() %>/api/eth_rpc">[ <%= gettext "Base URL:" %> <%= BlockScoutWeb.Endpoint.url() %>/api/eth_rpc ]</p>
       <p class="card-subtitle margin-bottom-0">
         <%= gettext "This API is provided to support some rpc methods in the exact format specified for ethereum nodes, which can be found " %> 
 

apps/block_scout_web/lib/block_scout_web/templates/api_docs/index.html.eex

@@ -2,7 +2,7 @@
   <div class="card">
     <div class="card-body">
       <h1 class="card-title margin-bottom-sm"><%= gettext("API Documentation") %></h2>
-      <p class="api-text-monospace" data-endpoint-url="<%= BlockScoutWeb.Endpoint.url() %>/api">[ <%= gettext "Base URL:" %> <%= @conn.host %>/api ]</p>
+      <p class="api-text-monospace" data-endpoint-url="<%= BlockScoutWeb.Endpoint.url() %>/api">[ <%= gettext "Base URL:" %> <%= BlockScoutWeb.Endpoint.url() %>/api ]</p>
       <p class="card-subtitle margin-bottom-0"><%= gettext "This API is provided for developers transitioning their applications from Etherscan to BlockScout. It supports GET and POST requests." %></p>
     </div>
     <div class="api-anchors-list">