swap chapters on signing components and data

book/source/07-signing_data.md

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+SPDX-FileCopyrightText: 2023 The "Notes on OpenPGP" project
+SPDX-License-Identifier: CC-BY-SA-4.0
+-->
+
+(signing_data)=
+# Signatures over data
+
+```{admonition} TODO
+:class: warning
+
+Add content, including:
+
+- Signature of a binary document
+
+- Signature of a canonical text document
+  - "The signature is calculated over the text data with its line endings converted to `<CR><LF>`"
+```
+
+## Data signatures
+
+A data signature serves the purpose to cryptographically guarantee the authenticity (and implicitly also the integrity) of a message, e.g. an email or a file, while a certification is used to attach metadata or subkeys to a certificate.
+Data signatures are always calculated by keys carrying the **S**igning key flag.
+Different types of signatures are distinguished by a signature type code and are calculated in different ways.
+Signatures can either be distributed standalone as *detached* signatures, or can be inlined with OpenPGP data, such as an OpenPGP message or a key or certificate.
+
+Data signatures (type 0x00 and 0x01) are created by hashing the message content and calculating a cryptographic signature over the hash.
+You can read more about data signatures in the [next chapter](signing_data).
+The result is packed up into an OpenPGP signature packet, which can either be included in the OpenPGP message (TODO: See section about forming messages, cleartext signature framework), or distributed separately as a so-called *detached* signature.
+Data signatures are always calculated using a **S**igning key.