fix(lapis-docs): mention how arrays must be supplied in form urlencoded requests

resolves #1089

Author: fengelniederhammer

.idea/runConfigurations/LapisOpen.xml

@@ -64,6 +64,8 @@ Check out the [fields](../references/fields) and [filters](../references/filters
 LAPIS also supports [URL encoded form data](https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST) for POST requests.
 The content type must be set to `application/x-www-form-urlencoded` and the query must be encoded as a query string.
 
+Note that arrays must be passed as repeated keys, e.g. `fields=country&fields=date`.
+
 :::tip
 This is useful if you want to send the query directly from a HTML form.
 If `<form>` element has the `method` attribute set to `POST`

lapis-docs/src/content/docs/concepts/request-methods.mdx

@@ -14,7 +14,7 @@ class FieldConverter(
     fun convert(source: String): Field {
         val cleaned = caseInsensitiveFieldsCleaner.clean(source)
             ?: throw BadRequestException(
-                "Unknown field: $source, known values are ${caseInsensitiveFieldsCleaner.getKnownFields()}",
+                "Unknown field: '$source', known values are ${caseInsensitiveFieldsCleaner.getKnownFields()}",
             )
 
         return Field(cleaned)

lapis/src/main/kotlin/org/genspectrum/lapis/request/Field.kt

@@ -445,7 +445,7 @@ class LapisControllerCommonFieldsTest(
             .andExpect(
                 jsonPath(
                     "\$.error.detail",
-                ).value(Matchers.containsString("Unknown field: nonExistingField, known values are [primaryKey,")),
+                ).value(Matchers.containsString("Unknown field: 'nonExistingField', known values are [primaryKey,")),
             )
     }