Enhanced security model / actual ReadOnly permission level

### Discussed in https://github.com/grafana/grafana/discussions/43487 <div type='discussions-op-text'> ^{Originally posted by **ppolewicz** December 22, 2021} ## What would you like to be added There is a pair of issues that are impractical to be discussed separately: 1. Grafana does not validate the request parameters (discussed in quite a few issues over the years, but #18157 seems to summarize it neatly) 2. Grafana allows the Viewer user to make any database query and not only those defined by dashboards and panels (reported in many places, but IMHO described best in [this comment](https://github.com/grafana/grafana/issues/26567#issuecomment-663354731)) The addition would be some kind of an OPTIONAL setting that would allow to use Grafana in a "really read only" mode, where only the queries written by the Dashboard designer can be executed by the user and only with parameters allowed by the Dashboard designer. ## Why is this needed (describe your use case and goals) For some installations it is impractical to separate the data into different databases for different users and being able to restrict who sees what is desired. There might be, I guess, a ton of issues related to the user being able to interact with a database directly. Those might not be officially classified as security today because the security model considers the Viewer user to be authorized to make any query to the database and but I don't want my service to be DoSed by a kid. ## How? The basic design is described [here](https://github.com/grafana/grafana/issues/18157#issuecomment-971033944), @torkelo [confirmed](https://github.com/grafana/grafana/issues/18157#issuecomment-971279650) that it is possible to implement it, though some restrictions might apply. That's fair and fine - depending on a setting, enhanced security might provide a more rigid structure in which not everything can be as easily achieveable as with the open model. We do expect that a dashboard with parameters filled wit…