refactor: renamed buckets;
fix: corrected Host header changing behavior in minio gin endpoint;
feat: function to convert local minio url to /s3/ path url with the backend host
feat: implemented registration emails;
fix: config variables for password length used the same env variable;
refactor: all available config variables added to docker-compose.yml
feat: helper function in errors for checking postgres error types;
feat: sql query method for finding users by their email;
feat: registration begin/complete with checking existing username/email;
refactor: error handling in controller
