Add documentation and tests for DQL - unique()

docs/docs/reference/functions.md

@@ -512,6 +512,14 @@ filter([1, 2, 3], (x) => x >= 2) = [2, 3]
 filter(["yes", "no", "yas"], (x) => startswith(x, "y")) = ["yes", "yas"]
 ```
 
+### `unique(array)`
+
+Creates a new array with only unique values. 
+
+```js
+unique([1, 3, 7, 3, 1]) => [1, 3, 7]
+```
+
 ### `map(array, func)`
 
 Applies the function to each element in the array, returning a list of the mapped results.

src/test/function/aggregation.test.ts

@@ -11,6 +11,13 @@ describe("filter()", () => {
     test("number list", () => expectEvals("filter(list(1, 2, 3), (k) => k >= 2)", [2, 3]));
 });
 
+describe("unique()", () => {
+    test("empty", () => expectEvals("unique([])", []));
+    test("single", () => expectEvals("unique([1])", [1]));
+    test("multiple unique", () => expectEvals("unique([1, 1, 1])", [1]));
+    test("multiple same", () => expectEvals("unique([1, 3, 7, 3, 1])", [1, 3, 7]));
+});
+
 describe("min()", () => {
     test("empty", () => expectEvals("min()", null));
     test("single", () => expectEvals("min(6)", 6));