doc: Explain to admins how to import data

docs/administrators/README.md

@@ -5,3 +5,4 @@
 - [Deploy in production](/docs/administrators/deploy.md)
 - [Deploy in production with Docker](/docs/administrators/docker.md)
 - [Changelog of Bileto](/CHANGELOG.md)
+- [Importing data](/docs/administrators/import-data.md)

docs/administrators/import-data.md

@@ -0,0 +1,36 @@
+# Importing data
+
+Bileto allows you to import data from a ZIP archive.
+
+To do so, run:
+
+```console
+www-data$ php bin/console app:data:import /path/to/archive.zip
+```
+
+The format of the archive is explained [in a document dedicated to developers.](/docs/developers/import-data.md)
+It allows you to import:
+
+- organizations;
+- roles;
+- users;
+- teams;
+- contracts;
+- labels;
+- and tickets with their messages, documents and spent time.
+
+Before importing the data into the database, the command performs some checks to verify the integrity and validity of the files to be imported.
+If at least one file is invalid, it fails.
+
+Also, the command detects if the data has already been imported to avoid to duplicate it.
+However, it doesn't update data already imported; it just ignores it.
+
+## Trusting documents mimetypes
+
+Users cannot upload some file types.
+However, if you import existing data and that you're sure the documents are safe, you can import documents that would not be accepted by Bileto otherwise.
+You must pass the `--trust-mimetypes` option to do so.
+
+```console
+www-data$ php bin/console app:data:import --trust-mimetypes /path/to/archive.zip
+```