Extend Adapter interface to include function to return adapter name

[lafriks]

Would be useful to allow check what adapter is used currently so that database type specific code could be executed only on right adapters.

func Name() string

or

func Type() string

that would return mysql, postgres, sqlite3 etc

[Fs02]

could you give examples?

and is the database type specific code will be in sql package?

[lafriks]

no it's for usage in user code later on, for one I would want this to use in migrator package for such code to be able to lock down migrations so that if multiple instances are started at same time (for example in containers) they would not run same migrations:

	if m.typ == DatabaseSQLite3 {
		if err := m.sync(ctx); err != nil {
			cancelUpdate(err)
		}
		return func(ctx context.Context, vers int64) {
			if vers == 0 {
				return
			}
			if err := m.repo.Insert(ctx, &version{Version: vers}); err != nil {
				cancelUpdate(err)
			}
		}, func() {}
	}

	updZeroVersion := "INSERT INTO versions(version, created_at) VALUES (0, current_timestamp) ON CONFLICT(version) DO UPDATE SET updated_at = current_timestamp"
	if m.typ == DatabaseMySQL {
		updZeroVersion = "INSERT INTO versions(version, created_at) VALUES (0, current_timestamp) ON DUPLICATE KEY UPDATE updated_at = current_timestamp"
	}

currently because of that I have to copy over migrator code and can not really implement it upstream as instead of go-rel/migration package: https://github.com/go-rel/migration/blob/dbef2632dc4efecbb107b4c61648a0d0d255c0ac/migration.go#L170
I use:

// New migratorr.
func New(typ string, repo rel.Repository) *Migrator {
	return &Migrator{
		typ:  typ,
		repo: repo,
	}
}

instead I could use for db specific code something like m.repo.Adapter().Type() == "sqlite3" instead of having to keep around current database type in code and pass it all around for database type specific SQLs etc

[Fs02]

got it, I think it's should be okay to add some metadata information like this

I prefer func Name() string, and maybe have a constant (ex: Name) in each adapter package so comparison can be done like: m.repo.Adapter().Type() == sqlite3.Name

[lafriks]

Ok, I will create PR

[lafriks]

@Fs02 please review:
#346
go-rel/sql#59
go-rel/sqlite3#53

If naming/implementation looks good I will create PRs for other adapters

[Fs02]

@lafriks need to be updated too
https://github.com/go-rel/reltest/blob/main/nop_adapter.go
https://github.com/go-rel/mssql