docs: expand reference pages and fix children shortcode rendering

Enable Goldmark block-level attributes so the relearn `children`
shortcode applies its CSS classes instead of printing them literally
in the table-of-contents pages. Also expand the deploy, plugins,
records, and email reference docs and add the checks pages.

content/reference/records/TXT.en.md

@@ -5,6 +5,40 @@ title: TXT
 weight: 20
 aliases:
     records/TXT
+description: "The TXT record attaches free-form text to a DNS name. Learn what it is used for and how happyDomain edits it through the Text Record service."
 ---
 
-Please, help us to write this Documentation screen
+A **TXT record** (defined in [RFC 1035](https://www.rfc-editor.org/rfc/rfc1035)) attaches one or more free-form text strings to a name in your zone. It carries no predefined meaning of its own, which makes it one of the most versatile record types: any application is free to define its own convention for the text it stores there.
+
+## Common uses
+
+Because a TXT record can hold arbitrary text, it has become the carrier for many widespread conventions:
+
+- **Domain ownership and site verification** — a provider asks you to publish a token so it can confirm you control the domain.
+- **SPF** — declares which servers are allowed to send e-mail for your domain.
+- **DKIM** — publishes the public key used to sign your outgoing e-mail.
+- **DMARC** — sets the policy applied when SPF or DKIM checks fail.
+- Various other key or policy publications defined by different tools.
+
+For most of these purposes, happyDomain offers dedicated, higher-level **services** (SPF, DKIM, DMARC, site verification, and more) that are easier and safer to use than a raw TXT record: they guide you with the right fields and validate the syntax for you. Browse them in the {{< relref "/reference/services" >}} chapter, in particular the e-mail-related services. Prefer those services whenever one matches your need.
+
+{{% notice style="info" title="When a TXT record becomes a service" %}}
+When happyDomain reads your zone, it recognises TXT records that follow a known convention (SPF, DKIM, DMARC, …) and presents them as their dedicated service rather than as a plain Text Record. Only TXT records without a recognised prefix or syntax are shown as a raw **Text Record**.
+{{% /notice %}}
+
+## Editing a TXT record in happyDomain
+
+In the zone editor, a plain TXT record appears as a **Text Record** service. It is intentionally minimal: a single field holds the text content of the record.
+
+To work with one:
+
+1. Open the subdomain where the record should live (the apex of the zone, or any subdomain such as `www`).
+2. Add or open the **Text Record** service.
+3. Type the full text string in its only field.
+4. Adjust the **TTL** if needed, then publish your changes to apply them.
+
+The value you enter is stored verbatim. Editing it and publishing updates the corresponding TXT record on that subdomain.
+
+{{% notice style="note" title="Long strings" %}}
+A single text string inside a TXT record cannot exceed 255 bytes at the DNS protocol level. Longer values are automatically split into 255-byte chunks for you. You simply enter the complete string in happyDomain — no manual splitting is required.
+{{% /notice %}}