https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/core/+/refs/heads/master/maintenance/tables.sql
ipblocks_restrictions

Table:
CREATE TABLE /*_*/ipblocks_restrictions (
  -- The ipb_id from ipblocks
  ir_ipb_id int NOT NULL,
  -- The restriction type id.
  ir_type tinyint(1) NOT NULL,
  -- The restriction id that corrposponds to the type. Typically a Page ID or a
  -- Namespace ID.
  ir_value int NOT NULL,
  PRIMARY KEY (ir_ipb_id, ir_type, ir_value)
) /*$wgDBTableOptions*/;

Example query
MariaDB [enwiki_p]> SELECT ir_ipb_id, CASE WHEN ( ir_type = 1 ) THEN 'page' ELSE 'namespace' END AS 'type', ir_value FROM ipblocks_restrictions LIMIT 25;
+-----------+-----------+----------+
| ir_ipb_id | type      | ir_value |
+-----------+-----------+----------+
|   9435157 | namespace |        4 |
|   9495590 | page      | 57861199 |
|   9497043 | page      | 30859855 |
|   9498101 | page      |  2333491 |
|   9498101 | page      | 42165878 |
|   9517403 | page      | 28280067 |
|   9517475 | page      |    50803 |
|   9517475 | page      |    87276 |
|   9517475 | page      | 19629641 |
|   9517475 | page      | 21347867 |
|   9517475 | page      | 23871476 |
|   9517475 | page      | 25169060 |
|   9517475 | page      | 61818020 |
|   9531962 | page      | 24758230 |
|   9533323 | page      |   497526 |
|   9536130 | page      |  2015570 |
|   9540101 | namespace |        0 |
|   9542727 | page      |   165094 |
|   9559276 | namespace |        0 |
|   9559540 | page      |   654157 |
|   9561071 | page      | 59625567 |
|   9561107 | page      | 62990726 |
|   9562223 | page      |   585629 |
|   9562223 | page      | 21486360 |
|   9563237 | page      | 34355486 |
+-----------+-----------+----------+

Note that:
`type` is either 1 or 2, shown as `page` or `namespace` to ease understanding
ir_value can only be an int, meaning that it cannot hold the action as a string
Multiple rows for a single block with multiple restrictions

Proposed implementation:
ActionRestriction, like for namespace / page

type: 3
ir_value - constant mapping with string to int, more added by hook (for thanks)

ActionRestriction::ACTION_CREATE_VALUE => 1
ActionRestriction::ACTION_UPLOAD_VALUE => 2

run hook

ACTION_THANK_VALUE = 101

Hook requires that no values override existing mapping
Values 1-100 are reserved for core

+-----------+-----------+----------+
| ir_ipb_id | type      | ir_value |
+-----------+-----------+----------+
|   9562223 | action    |        1 |
|   9562223 | action    |        2 |
|   9563237 | action    |      101 |
+-----------+-----------+----------+

^ 1 block from creating and uploading, and another block from thanks