docs/blobs: reword to avoid any misunderstandings

Author: FliegendeWurst

docs/Developer Guide/Developer Guide/Development and architecture/Database/blobs.md

@@ -1,2 +1,7 @@
 # blobs
-<figure class="table"><table><thead><tr><th>Column Name</th><th>Data Type</th><th>Nullity</th><th>Default value</th><th>Description</th></tr></thead><tbody><tr><th><code>blobId</code></th><td>Text</td><td>Non-null</td><td>&nbsp;</td><td>The unique ID of the blob (e.g. <code>XXbfAJXqWrYnSXcelLFA</code>).</td></tr><tr><th><code>content</code></th><td>Text</td><td>Nullable</td><td><code>null</code></td><td><p>The content of the blob, can be either:</p><ul><li>text (for plain text notes or HTML notes).</li><li>binary (for images and other types of attachments)</li></ul></td></tr><tr><th><code>dateModified</code></th><td>Text</td><td>Non-null</td><td>&nbsp;</td><td>Localized modification date (e.g. <code>2023-11-08 18:43:44.204+0200</code>)</td></tr><tr><th><code>utcDateModified</code></th><td>Text</td><td>Non-null</td><td>&nbsp;</td><td>Modification date in UTC format (e.g. <code>2023-11-08 16:43:44.204Z</code>)</td></tr></tbody></table></figure>
+<figure class="table"><table><thead><tr><th>Column Name</th><th>Data Type</th><th>Nullity</th><th>Default value</th><th>Description</th></tr></thead><tbody><tr><th><code>blobId</code></th><td>Text</td><td>Non-null</td><td>&nbsp;</td><td>The unique ID of the blob (e.g. <code>XXbfAJXqWrYnSXcelLFA</code>).
+
+Important: this ID is actually a hash of the content, see <code>AbstractBeccaEntity#saveBlob</code>! It is a logic error to modify an existing blob.
+</td></tr><tr><th><code>content</code></th><td>Text</td><td>Nullable</td><td><code>null</code></td><td><p>The content of the blob, can be either:</p><ul><li>text (for plain text notes or HTML notes).</li><li>binary (for images and other types of attachments)</li></ul></td></tr><tr><th><code>dateModified</code></th><td>Text</td><td>Non-null</td><td>&nbsp;</td><td>Creation date with timezone offset (e.g. <code>2023-11-08 18:43:44.204+0200</code>)</td></tr><tr><th><code>utcDateModified</code></th><td>Text</td><td>Non-null</td><td>&nbsp;</td><td>Creation date in UTC format (e.g. <code>2023-11-08 16:43:44.204Z</code>).
+
+Blobs cannot be modified, so this timestamp specifies when the blob was created.</td></tr></tbody></table></figure>