feat(lapis2-docs): document url encoded forms

resolves #765

lapis2-docs/src/components/RenderedExampleForm.astro

@@ -0,0 +1,20 @@
+---
+import { getConfig } from '../config';
+import { getLapisUrl } from '../lapisUrl';
+
+const firstMetadatum = getConfig().schema.metadata[0];
+const lapisUrl = getLapisUrl();
+
+const html = String.raw`<form action="${lapisUrl}/sample/aggregated" method="POST">
+    <label>
+        Field to aggregate by:
+        <input type="text" name="fields" value="${firstMetadatum.name}" />
+    </label>
+    <input type="hidden" name="downloadAsFile" value="true" />
+    <input type="submit" value="Submit" />
+</form>`;
+---
+
+<pre><code>{html}</code></pre>
+
+<div set:html={html} />

lapis2-docs/src/content/docs/concepts/request-methods.mdx

@@ -5,6 +5,7 @@ description: Request methods
 
 import TabsBox from '../../../components/TabsBox/astro/TabsBox.astro';
 import Tab from '../../../components/TabsBox/astro/Tab.astro';
+import RenderedExampleForm from '../../../components/RenderedExampleForm.astro';
 
 LAPIS supports queries via GET and POST requests. GET requests encode the query in the URL, offering a simple, shareable
 format ideal for direct browser access. Most features are supported with GET requests. POST requests requires formatting
@@ -57,3 +58,19 @@ example code for doing it with curl and from R and Python:
 This is a general example and will only work on instances that have the fields `region`, `country`, and `date`.
 Check out the [fields](../references/fields/) and [filters](../references/filters/) page to see information about this instance.
 :::
+
+## URL Encoded Form Data
+
+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.
+
+:::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`
+and the `enctype` attribute set to `application/x-www-form-urlencoded` (which is the default value),
+then the `<form>` element will send the data as URL encoded form data.
+:::
+
+### Example
+
+<RenderedExampleForm />