Add worker tagging (#862)

This allows workers to have tags assigned to them, which can then be filtered to control which targets they are allowed to serve.

internal/db/schema/migrations/postgres/0/41_targets.up.sql

@@ -154,6 +154,7 @@ before insert on target_tcp
 
 
 -- target_all_subtypes is a union of all target subtypes 
+-- NOTE: this is replaced in 100 to add worker_filter
 create view target_all_subtypes
 as 
 select 

internal/db/schema/migrations/postgres/0/50_session.up.sql

@@ -158,6 +158,7 @@ begin;
     endpoint text -- not part of the warehouse, used to send info to the worker
   );
 
+  -- Replaced in 100 to add worker_filter
   create trigger 
     immutable_columns
   before
@@ -453,6 +454,7 @@ begin;
   create trigger insert_session_state before insert on session_state
     for each row execute procedure insert_session_state();
 
+  -- Replaced in 100 to add worker_filter
   create view session_with_state as
   select
     s.public_id,

internal/db/schema/migrations/postgres/dev/01_server_tags_migrations.down.sql

@@ -0,0 +1,8 @@
+begin;
+
+drop domain wt_bexprfilter;
+
+drop table server_tag;
+drop domain wt_tagpair;
+
+commit;

internal/db/schema/migrations/postgres/dev/01_server_tags_migrations.up.sql

@@ -0,0 +1,123 @@
+begin;
+
+-- This series of expressions fixes the primary key on the server table
+alter table session
+  drop constraint session_server_id_server_type_fkey;
+alter table server
+  drop constraint server_pkey;
+alter table server
+  drop column name;
+alter table server
+  add primary key (private_id);
+alter table server
+  add constraint server_id_must_not_be_empty
+  check(length(trim(private_id)) > 0);
+alter table session
+  add constraint session_server_id_fkey
+  foreign key (server_id)
+  references server(private_id)
+  on delete set null
+  on update cascade;
+
+create domain wt_bexprfilter as text
+check(
+  value is null
+    or
+    (
+      length(trim(value)) > 0
+        and
+      length(trim(value)) <= 2048
+    )
+);
+comment on domain wt_bexprfilter is
+  'Text field with constraints for go-bexpr filters';
+
+-- Add the worker filter to the target_tcp table and session table
+alter table target_tcp
+  add column worker_filter wt_bexprfilter;
+alter table session
+  add column worker_filter wt_bexprfilter;
+
+-- Replace the immutable columns trigger from 50 to add worker_filter
+drop trigger immutable_columns on session;
+create trigger immutable_columns
+  before update on session
+    for each row execute procedure immutable_columns('public_id', 'certificate', 'expiration_time', 'connection_limit', 'create_time', 'endpoint', 'worker_filter');
+
+-- Replaces the view created in 41 to include worker_filter
+drop view target_all_subtypes;
+create view target_all_subtypes
+as
+select
+  public_id,
+  scope_id,
+  name,
+  description,
+  default_port,
+  session_max_seconds,
+  session_connection_limit,
+  version,
+  create_time,
+  update_time,
+  worker_filter,
+  'tcp' as type
+from target_tcp;
+
+-- Replaces the view created in 50 to include worker_filter
+drop view session_with_state;
+create view session_with_state as
+  select
+    s.public_id,
+    s.user_id,
+    s.host_id,
+    s.server_id,
+    s.server_type,
+    s.target_id,
+    s.host_set_id,
+    s.auth_token_id,
+    s.scope_id,
+    s.certificate,
+    s.expiration_time,
+    s.connection_limit,
+    s.tofu_token,
+    s.key_id,
+    s.termination_reason,
+    s.version,
+    s.create_time,
+    s.update_time,
+    s.endpoint,
+    s.worker_filter,
+    ss.state,
+    ss.previous_end_time,
+    ss.start_time,
+    ss.end_time
+  from
+    session s,
+    session_state ss
+  where
+    s.public_id = ss.session_id;
+
+create domain wt_tagpair as text
+check(
+  value is not null
+    and
+  length(trim(value)) > 0
+    and
+  length(trim(value)) <= 512
+    and
+  lower(trim(value)) = value
+);
+comment on domain wt_tagpair is
+  'Text field with constraints for key/value pairs';
+
+create table server_tag (
+  server_id text
+    references server(private_id)
+    on delete cascade
+    on update cascade,
+  key wt_tagpair,
+  value wt_tagpair,
+  primary key(server_id, key, value)
+);
+
+commit;