Allow annotation on TERARium artifacts

[YohannParis]

Design out the capability to add "notes" to an artifact. We want to be able to record

• Artifact type
• Artifact id
• Timestamp
• UserID
• Annotation type
• Annotation content

[mwdchang]

I am going to close this as technically the plumbing and APIs are more or less in place /api/annotations.

terarium=# \d+ annotation
                                                    Table "public.annotation"
     Column      |          Type          | Collation | Nullable | Default | Storage  | Compression | Stats target | Description
-----------------+------------------------+-----------+----------+---------+----------+-------------+--------------+-------------
 id              | character varying(255) |           | not null |         | extended |             |              |
 artifactid      | character varying(255) |           |          |         | extended |             |              |
 artifacttype    | character varying(255) |           |          |         | extended |             |              |
 content         | text                   |           |          |         | extended |             |              |
 projectid       | bigint                 |           |          |         | plain    |             |              |
 timestampmillis | bigint                 |           | not null |         | plain    |             |              |
 username        | character varying(255) |           | not null |         | extended |             |              |