Fix some things that were broken

[hasezoey]

This PR is a small collection of fixes from #104, but refactored to current state dsync and separate from the other changes and not being based on #103, in more detail:

• always have type ConnectionType be public (was broken for once-connection-type)
• change serde derives to use serde:: instead of requiring it to be imported (was broken for once-common-structs)

these things would likely be catched earlier if the tests would actually be compile tested

[hasezoey]

as this pr is a collection of fixes, i added some things i noticed while doing #114, namely:

• i noticed that diesel:PgConnection does not actually exist (at least not anymore)
• that tables which names will be converted will have mismatching imports (directory / module is name tableA while the import was table_a)
• added a TODO because i also noticed that the delete pass does not check single-model-file files

[Wulf]

Looks good to me! Let's merge this in instead of #104

[Wulf]

I'm going to add a few more commits here which should take care of some of the chnages which weren't included from #104

[Wulf]

ah, I can't seem to do this. Do you mind adding the following changes?

1. Remove 'tsync' from Cargo.toml

2. In src/lib.rs, add the following comment above pub connection_type: String,:

    /// For example:
    /// - `diesel::pg::PgConnection` (default)
    /// - `diesel::sqlite::SqliteConnection`
    /// - `diesel::mysql::MysqlConnection`
    /// - or, your custom diesel connection type (struct which implements `diesel::connection::Connection`)

3. In src/lib.rs, add a default for GenerationConfig before impl GenerationConfig<'_> {

impl<'a> Default for GenerationConfig<'a> {
    fn default() -> Self {
        Self {
            table_options: Default::default(),
            default_table_options: Default::default(),
            connection_type: "diesel::pg::PgConnection".into(),
            diesel_backend: "diesel::pg::Pg".into(),
            schema_path: "crate::schema::".into(),
            model_path: "crate::models::".into(),
            once_common_structs: true,
            once_connection_type: true,
        }
    }
}

Aaandddd, that should be all! 🙌

If you're not able to do this, no worries, I can add it in after we merge this in. Just let me know!

[hasezoey]

rebased on latest main, and added the 2. for examples, removing the (default) and adding r2d2, also adding that comment to the binary help.
i also changed the previous diesel::prelude::PgConnection to diesel::pg::PgConnection (as requested in #114 (comment))

as for 1. remove tsync feature default and 3. GenerationConfig default derive, this should likely be done in a separate PR
(the tsync attribute is not added by default and would require a argument (--tsync) in addition to having the feature enabled; generation config default derive would likely need some refactoring to make it work with good defaults (like connection_type)