sqldb: add invoice events SQL schema

sqldb/sqlc/migrations/000003_invoice_events.down.sql

@@ -0,0 +1,9 @@
+DROP TABLE IF EXISTS invoice_events;
+
+DROP INDEX IF EXISTS invoice_events_created_at_idx;
+DROP INDEX IF EXISTS invoice_events_invoice_id_idx;
+DROP INDEX IF EXISTS invoice_events_htlc_id_idx;
+DROP INDEX IF EXISTS invoice_events_set_id_idx;
+DROP INDEX IF EXISTS invoice_events_event_type_idx;
+
+DROP TABLE IF EXISTS invoice_event_types;

sqldb/sqlc/migrations/000003_invoice_events.up.sql

@@ -0,0 +1,59 @@
+-- invoice_event_types stores the different types of events that can be emitted 
+-- for invoices.
+CREATE TABLE IF NOT EXISTS invoice_event_types(
+    id INTEGER PRIMARY KEY,
+
+    description TEXT NOT NULL
+);
+
+-- invoice_events stores all events related to the node invoices.
+CREATE TABLE IF NOT EXISTS invoice_events (
+    id INTEGER PRIMARY KEY,
+
+    -- created_at is the creation time of this event.
+    created_at TIMESTAMP NOT NULL,
+
+    -- invoice_id is the reference to the invoice this event was emitted for.
+    invoice_id INTEGER NOT NULL REFERENCES invoices(id),
+
+    -- htlc_id is the reference to the htlc this event was emitted for, may be 
+    -- null.
+    htlc_id BIGINT REFERENCES invoice_htlcs(htlc_id),
+
+    -- set_id is the reference to the set_id this event was emitted for, may be
+    -- null.
+    set_id BLOB NOT NULL REFERENCES amp_invoice_payments(set_id),
+
+    -- event_type is the type of this event.
+    event_type INTEGER NOT NULL REFERENCES invoice_event_types(id),
+
+    -- event_metadata is a TLV encoding any relevant information for this kind 
+    -- of events.
+    event_metadata BLOB
+);
+
+CREATE INDEX IF NOT EXISTS invoice_events_created_at_idx ON invoice_events(created_at);
+CREATE INDEX IF NOT EXISTS invoice_events_invoice_id_idx ON invoice_events(invoice_id);
+CREATE INDEX IF NOT EXISTS invoice_events_htlc_id_idx ON invoice_events(htlc_id);
+CREATE INDEX IF NOT EXISTS invoice_events_set_id_idx ON invoice_events(set_id);
+CREATE INDEX IF NOT EXISTS invoice_events_event_type_idx ON invoice_events(event_type);
+
+
+-- invoice_event_types defines the different types of events that can be emitted
+-- for an invoice.
+INSERT INTO invoice_event_types (id, description) 
+VALUES 
+    -- invoice_created is the event emitted when an invoice is created.
+    (0, 'invoice_created'), 
+    -- invoice_canceled is the event emitted when an invoice is canceled.
+    (1, "invoice_canceled"), 
+    -- invoice_settled is the event emitted when an invoice is settled.
+    (2, "invoice_settled"),
+    -- setid_created is the event emitted when the first htlc for the set_id is 
+    -- received. 
+    (3, "setid_created"),
+    -- setid_canceled is the event emitted when the set_id is canceled.
+    (4, "setid_canceled"),
+    -- setid_settled is the event emitted when the set_id is settled.
+    (5, "setid_settled");
+