Add languages

20230125152306_languages.down.sql

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+BEGIN;
+DROP TABLE languages;
+COMMIT;

20230125152306_languages.up.sql

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+BEGIN;
+
+CREATE TABLE languages (
+    id BIGSERIAL PRIMARY KEY,
+    code VARCHAR(2) NOT NULL,
+    english_name VARCHAR NOT NULL,
+    self_name VARCHAR NOT NULL,
+    CONSTRAINT code_is_language_code CHECK (is_language_code(code)),
+    CONSTRAINT english_name_is_name CHECK (is_name(english_name)),
+    CONSTRAINT self_name_is_name CHECK (is_name(self_name))
+);
+
+CREATE UNIQUE INDEX languages_code ON languages (code);
+CREATE UNIQUE INDEX languages_english_name ON languages (english_name);
+
+INSERT INTO languages (code, english_name, self_name) VALUES
+    ('en', 'English',  'English'),
+    ('ru', 'Russian',  'Русский'),
+    ('pl', 'Polish',   'Polski'),
+    ('es', 'Spanish',  'Español'),
+    ('ka', 'Georgian', 'ქართული');
+
+COMMIT;