feat(knex): create database interfaces and knexjs nest integration

Co-authored-by: Philip Molares <philip.molares@udo.edu>
Signed-off-by: Philip Molares <philip.molares@udo.edu>
Signed-off-by: Erik Michelson <github@erik.michelson.eu>

backend/src/config/database.config.ts

@@ -5,6 +5,7 @@
  */
 import { registerAs } from '@nestjs/config';
 import z from 'zod';
+import { Knex } from 'knex';
 
 import { DatabaseType } from './database-type.enum';
 import { parseOptionalNumber } from './utils';
@@ -90,3 +91,39 @@ export default registerAs('databaseConfig', () => {
   }
   return databaseConfig.data;
 });
+
+export function getKnexConfig(databaseConfig: DatabaseConfig): Knex.Config {
+  switch (databaseConfig.type) {
+    case DatabaseType.SQLITE:
+      return {
+        client: 'better-sqlite3',
+        connection: {
+          filename: databaseConfig.database,
+        },
+      };
+    case DatabaseType.POSTGRES:
+      return {
+        client: 'pg',
+        connection: {
+          host: databaseConfig.host,
+          port: databaseConfig.port,
+          user: databaseConfig.username,
+          database: databaseConfig.database,
+          password: databaseConfig.password,
+          // eslint-disable-next-line @typescript-eslint/naming-convention
+          application_name: 'HedgeDoc',
+        },
+      };
+    case DatabaseType.MARIADB:
+      return {
+        client: 'mysql',
+        connection: {
+          host: databaseConfig.host,
+          port: databaseConfig.port,
+          user: databaseConfig.username,
+          database: databaseConfig.database,
+          password: databaseConfig.password,
+        },
+      };
+  }
+}