Reduce the surface area of the configuration crate. (#297)

### What

This makes a few changes to the configuration (version 3) to reduce the
surface area.

All changes are refactors.

### How

1. `unqualified_schemas` was deprecated and has been removed.
2. `set_connection_uri` is only used in tests, so I moved it to the
tests.
3. `ConfigureOptions` has been moved to its own file to keep things a
bit more private.
4. Other functions have been made private.
5. When configuring, we avoid cloning where possible.

crates/configuration/src/configuration.rs

@@ -85,16 +85,3 @@ pub fn as_runtime_configuration(input: &Configuration) -> RuntimeConfiguration<'
         },
     }
 }
-
-// for tests
-
-pub fn set_connection_uri(input: RawConfiguration, connection_uri: String) -> RawConfiguration {
-    match input {
-        RawConfiguration::Version3(config) => {
-            RawConfiguration::Version3(version3::RawConfiguration {
-                connection_uri: ConnectionUri::Uri(ResolvedSecret(connection_uri)),
-                ..config
-            })
-        }
-    }
-}

crates/configuration/src/lib.rs

@@ -4,8 +4,8 @@ mod values;
 pub mod version3;
 
 pub use configuration::{
-    as_runtime_configuration, configure, set_connection_uri, validate_raw_configuration,
-    Configuration, RawConfiguration, RuntimeConfiguration,
+    as_runtime_configuration, configure, validate_raw_configuration, Configuration,
+    RawConfiguration, RuntimeConfiguration,
 };
 pub use values::{ConnectionUri, IsolationLevel, PoolSettings, ResolvedSecret};
 pub use version3::occurring_scalar_types;

crates/configuration/src/values/mod.rs

@@ -1,10 +1,8 @@
-mod comparison;
 mod isolation_level;
 mod pool_settings;
 mod secret;
 mod uri;
 
-pub use comparison::ComparisonOperatorMapping;
 pub use isolation_level::IsolationLevel;
 pub use pool_settings::PoolSettings;
 pub use secret::ResolvedSecret;