docs: Add documentation about internal server endpoints

Author: oxyno-zeta

docs/feature-guide/internal-api.md

@@ -0,0 +1,200 @@
+# Internal API
+
+This API is served by the internal server port and shouldn't be public. The aim of this one it to provide internal services like monitoring, health status or debug configuration.
+
+## /health
+
+This endpoint will give the status of the application. This will either answer with
+
+- a 200 status code and a json body when everything is ok
+- a 500 status code and a json body explaining why there is a problem
+
+## /metrics
+
+This endpoint will give metrics with the prometheus format.
+
+## /config
+
+This endpoint will show the latest configuration loaded by the application. Data are changed each time application is reloading the configuration.
+
+Everything is shown in json format with the same keys are in the yaml configuration files.
+
+Important note: Secret values aren't displayed. Only environment variable names and file paths.
+
+Here is a payload example:
+
+```json
+{
+  "config": {
+    "log": { "level": "info", "format": "json", "filePath": "" },
+    "tracing": {
+      "fixedTags": null,
+      "flushInterval": "",
+      "udpHost": "",
+      "queueSize": 0,
+      "enabled": false,
+      "logSpan": false
+    },
+    "metrics": { "disableRouterPath": false },
+    "server": {
+      "timeouts": {
+        "readTimeout": "",
+        "readHeaderTimeout": "60s",
+        "writeTimeout": "",
+        "idleTimeout": ""
+      },
+      "cors": null,
+      "cache": null,
+      "compress": {
+        "enabled": true,
+        "types": [
+          "text/html",
+          "text/css",
+          "text/plain",
+          "text/javascript",
+          "application/javascript",
+          "application/x-javascript",
+          "application/json",
+          "application/atom+xml",
+          "application/rss+xml",
+          "image/svg+xml"
+        ],
+        "level": 5
+      },
+      "ssl": null,
+      "listenAddr": "",
+      "port": 8080
+    },
+    "internalServer": {
+      "timeouts": {
+        "readTimeout": "",
+        "readHeaderTimeout": "60s",
+        "writeTimeout": "",
+        "idleTimeout": ""
+      },
+      "cors": null,
+      "cache": null,
+      "compress": {
+        "enabled": true,
+        "types": [
+          "text/html",
+          "text/css",
+          "text/plain",
+          "text/javascript",
+          "application/javascript",
+          "application/x-javascript",
+          "application/json",
+          "application/atom+xml",
+          "application/rss+xml",
+          "image/svg+xml"
+        ],
+        "level": 5
+      },
+      "ssl": null,
+      "listenAddr": "",
+      "port": 9090
+    },
+    "targets": {
+      "test": {
+        "bucket": {
+          "credentials": null,
+          "requestConfig": null,
+          "name": "bucket1",
+          "prefix": "",
+          "region": "us-east-1",
+          "s3Endpoint": "",
+          "s3ListMaxKeys": 1000,
+          "s3MaxUploadParts": 10000,
+          "s3UploadPartSize": 5,
+          "s3UploadConcurrency": 5,
+          "s3UploadLeavePartsOnError": false,
+          "disableSSL": false,
+          "credentials": {
+            "accessKey": { "env": "FAKE", "path": "" },
+            "secretKey": { "path": "/secret", "env": "" }
+          }
+        },
+        "resources": null,
+        "mount": { "host": "", "path": ["/test/"] },
+        "actions": {
+          "GET": { "config": null, "enabled": true },
+          "PUT": null,
+          "DELETE": null
+        },
+        "templates": {
+          "folderList": null,
+          "notFoundError": null,
+          "internalServerError": null,
+          "forbiddenError": null,
+          "unauthorizedError": null,
+          "badRequestError": null,
+          "put": null,
+          "delete": null,
+          "helpers": null
+        },
+        "keyRewriteList": null
+      }
+    },
+    "templates": {
+      "folderList": {
+        "path": "templates/folder-list.tpl",
+        "headers": {
+          "Content-Type": "{{ template \"main.headers.contentType\" . }}"
+        },
+        "status": "200"
+      },
+      "targetList": {
+        "path": "templates/target-list.tpl",
+        "headers": {
+          "Content-Type": "{{ template \"main.headers.contentType\" . }}"
+        },
+        "status": "200"
+      },
+      "notFoundError": {
+        "path": "templates/not-found-error.tpl",
+        "headers": {
+          "Content-Type": "{{ template \"main.headers.contentType\" . }}"
+        },
+        "status": "404"
+      },
+      "internalServerError": {
+        "path": "templates/internal-server-error.tpl",
+        "headers": {
+          "Content-Type": "{{ template \"main.headers.contentType\" . }}"
+        },
+        "status": "500"
+      },
+      "unauthorizedError": {
+        "path": "templates/unauthorized-error.tpl",
+        "headers": {
+          "Content-Type": "{{ template \"main.headers.contentType\" . }}"
+        },
+        "status": "401"
+      },
+      "forbiddenError": {
+        "path": "templates/forbidden-error.tpl",
+        "headers": {
+          "Content-Type": "{{ template \"main.headers.contentType\" . }}"
+        },
+        "status": "403"
+      },
+      "badRequestError": {
+        "path": "templates/bad-request-error.tpl",
+        "headers": {
+          "Content-Type": "{{ template \"main.headers.contentType\" . }}"
+        },
+        "status": "400"
+      },
+      "put": { "path": "templates/put.tpl", "headers": {}, "status": "204" },
+      "delete": {
+        "path": "templates/delete.tpl",
+        "headers": {},
+        "status": "204"
+      },
+      "helpers": ["templates/_helpers.tpl"]
+    },
+    "authProviders": null,
+    "listTargets": { "mount": null, "resource": null, "enabled": false }
+  }
+}
+```