Fix most glaring bugs and vulnerabilities

postgres/init/020_dictionary_export.sql

@@ -0,0 +1,19 @@
+CREATE TYPE dictionary_export_status AS ENUM ('pending', 'in progress', 'failed', 'finished');
+
+CREATE TYPE dictionary_export_file_format AS ENUM ('xml', 'csv', 'tsv', 'tbx');
+
+CREATE TABLE dictionary_export (
+  id INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+  dictionary_id INT NOT NULL REFERENCES dictionary ON DELETE CASCADE, -- Consider indexing this one, since you're making queries with it in a WHERE clause and since deletion of rows from dictionary will require a scan of this table for references.
+  status dictionary_export_status NOT NULL DEFAULT 'pending',
+  time_created TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  time_started TIMESTAMPTZ,
+  time_finished TIMESTAMPTZ,
+  entry_count INT,
+  is_valid_filter BOOL,
+  is_published_filter BOOL,
+  is_terminology_reviewed_filter BOOL,
+  is_language_reviewed_filter BOOL,
+  status_filter entry_status,
+  export_file_format dictionary_export_file_format NOT NULL
+);