Use an enum instead of a boolean to differentiate search

It's not very likely to have more modes of search besides normal and
trashed, but got surprised in that way quite often and it's nicer this
way anyways.

modules/restapi/src/main/resources/docspell-openapi.yml

@@ -1478,7 +1478,7 @@ paths:
         - $ref: "#/components/parameters/limit"
         - $ref: "#/components/parameters/offset"
         - $ref: "#/components/parameters/withDetails"
-        - $ref: "#/components/parameters/deleted"
+        - $ref: "#/components/parameters/searchMode"
       responses:
         200:
           description: Ok
@@ -4114,12 +4114,16 @@ components:
         withDetails:
           type: boolean
           default: false
-        deleted:
-          type: boolean
-          default: false
+        searchMode:
+          type: string
+          format: searchmode
+          enum:
+            - normal
+            - trashed
+          default: normal
           description: |
-            If this is true, the search performed only for
-            soft-deleted items.
+            Specify whether the search query should apply to
+            soft-deleted items or not.
         query:
           type: string
           description: |
@@ -5846,12 +5850,13 @@ components:
       description: Whether to return details to each item.
       schema:
         type: boolean
-    deleted:
-      name: deleted
+    searchMode:
+      name: searchMode
       in: query
       description: Whether to search in soft-deleted items only.
       schema:
-        type: boolean
+        type: string
+        format: searchmode
     name:
       name: name
       in: path