Search: Added structure for search term inputs

Sets things up to allow more complex terms ready to handle negation.

app/Search/SearchOptionSet.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace BookStack\Search;
+
+class SearchOptionSet
+{
+    /**
+     * @var SearchOption[]
+     */
+    public array $options = [];
+
+    public function __construct(array $options = [])
+    {
+        $this->options = $options;
+    }
+
+    public function toValueArray(): array
+    {
+        return array_map(fn(SearchOption $option) => $option->value, $this->options);
+    }
+
+    public function toValueMap(): array
+    {
+        $map = [];
+        foreach ($this->options as $key => $option) {
+            $map[$key] = $option->value;
+        }
+        return $map;
+    }
+
+    public function merge(SearchOptionSet $set): self
+    {
+        return new self(array_merge($this->options, $set->options));
+    }
+
+    public function filterEmpty(): self
+    {
+        $filteredOptions = array_filter($this->options, fn (SearchOption $option) => !empty($option->value));
+        return new self($filteredOptions);
+    }
+
+    public static function fromValueArray(array $values): self
+    {
+        $options = array_map(fn($val) => new SearchOption($val), $values);
+        return new self($options);
+    }
+
+    public static function fromMapArray(array $values): self
+    {
+        $options = [];
+        foreach ($values as $key => $value) {
+            $options[$key] = new SearchOption($value);
+        }
+        return new self($options);
+    }
+}