feat: better database errors (#2109)

* feat(core): create error kind enum

* feat(core): add error kind for postgres

* feat(core): add error kind for sqlite

* feat(core): add error kind for mysql

* test(postgres): add error tests

* test(sqlite): add error tests

* test(mysql): add error tests

* fix(tests): fix tests rebasing

* refac(errors): add `ErrorKind::Other` variant

tests/sqlite/setup.sql

@@ -8,6 +8,16 @@ CREATE TABLE tweet (
 INSERT INTO tweet(id, text, owner_id)
 VALUES (1, '#sqlx is pretty cool!', 1);
 --
+CREATE TABLE tweet_reply (
+    id BIGINT NOT NULL PRIMARY KEY,
+    tweet_id BIGINT NOT NULL,
+    text TEXT NOT NULL,
+    owner_id BIGINT,
+    CONSTRAINT tweet_id_fk FOREIGN KEY (tweet_id) REFERENCES tweet(id)
+);
+INSERT INTO tweet_reply(id, tweet_id, text, owner_id)
+VALUES (1, 1, 'Yeah! #sqlx is indeed pretty cool!', 1);
+--
 CREATE TABLE accounts (
     id INTEGER NOT NULL PRIMARY KEY,
     name TEXT NOT NULL,
@@ -18,3 +28,10 @@ VALUES (1, 'Herp Derpinson', 1);
 CREATE VIEW accounts_view as
 SELECT *
 FROM accounts;
+--
+CREATE TABLE products (
+    product_no INTEGER,
+    name TEXT,
+    price NUMERIC,
+    CONSTRAINT price_greater_than_zero CHECK (price > 0)
+);