[Bug]: Nil pointer dereference in ToDockerV2AuthString() #97

Description

In pkg/provider/models/models.go (lines 108-110), there's a nil check for Username but not for Password. If a user provides a username without a password, the code will panic.

Location: pkg/provider/models/models.go:108-110

if r.Username != nil {
    authConfig.Username = *r.Username
    authConfig.Password = *r.Password  // panic if Password is nil
}

Expected behavior

Add nil check for Password:

if r.Username != nil && r.Password != nil {
    authConfig.Username = *r.Username
    authConfig.Password = *r.Password
}