dashboard: a subscribed node's message written out, read from it when shown

A subscribed node's messages come without being written out (their stream leaves the
text out: up to 8 KiB each, 500 at a time), so the figures box said only when, both
ends, type and size of one. Now the node answers for one message by its number,
`GET /admin/dashboard/messages/own/{seq}` (`{"text": …}`, `404` once it isn't kept),
which pages of other origins may call as they do its streams (`cors::open`), and the
page reads it when the message is shown, with its narrow token, and keeps it on the
message. Where it can't be read, the box says why.

1 files changed, 27 insertions, 0 deletions

diff --git a/docs/openapi.yaml b/docs/openapi.yaml
index 0fad136..03afa2f 100644
--- a/docs/openapi.yaml
+++ b/docs/openapi.yaml
@@ -1293,6 +1293,33 @@ paths:
         '401':
           $ref: '#/components/responses/Unauthorized'
 
+  /admin/dashboard/messages/own/{seq}:
+    get:
+      tags: [Admin]
+      summary: One of this node's messages, written out
+      description: |
+        The message `seq` (its number in `messages/own/events`) written out, as this
+        node's own console shows it, for a page subscribed to this node showing it (CORS,
+        with a token). Kept while the message log is: the latest 1000, while one looks.
+      parameters:
+        - name: seq
+          in: path
+          required: true
+          schema: { type: integer }
+      responses:
+        '200':
+          description: The message written out.
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  text: { type: string }
+        '401':
+          $ref: '#/components/responses/Unauthorized'
+        '404':
+          description: Not kept any more.
+
   /admin/dashboard/refresh:
     post:
       tags: [Admin]