config options for log format and color usage

We want to be able to disable colors for complement logs (since they
are likely to be opened in a text editor). There's no pressing need for
alternative log formats, but I'm interested in whether the 'pretty'
format will be easier for debugging.

I chose to add 'log_*' options rather than making a separate 'log'
section for now. There's been some discussion about trying to separate
the tracing/logging stuff into more structured sections, but that can
happen later.

src/config.rs

@@ -77,6 +77,10 @@ pub(crate) struct Config {
     pub(crate) trusted_servers: Vec<OwnedServerName>,
     #[serde(default = "default_log")]
     pub(crate) log: EnvFilterClone,
+    #[serde(default = "true_fn")]
+    pub(crate) log_colors: bool,
+    #[serde(default)]
+    pub(crate) log_format: LogFormat,
     #[serde(default)]
     pub(crate) turn_username: String,
     #[serde(default)]
@@ -110,6 +114,20 @@ pub(crate) enum ListenConfig {
     },
 }
 
+#[derive(Copy, Clone, Default, Debug, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub(crate) enum LogFormat {
+    /// Use the [`tracing_subscriber::fmt::format::Pretty`] formatter
+    Pretty,
+    /// Use the [`tracing_subscriber::fmt::format::Full`] formatter
+    #[default]
+    Full,
+    /// Use the [`tracing_subscriber::fmt::format::Compact`] formatter
+    Compact,
+    /// Use the [`tracing_subscriber::fmt::format::Json`] formatter
+    Json,
+}
+
 impl Display for ListenConfig {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {

src/observability.rs

@@ -23,7 +23,11 @@ use tokio::time::Instant;
 use tracing_flame::{FlameLayer, FlushGuard};
 use tracing_subscriber::{layer::SubscriberExt, EnvFilter, Layer, Registry};
 
-use crate::{config::Config, error, utils::error::Result};
+use crate::{
+    config::{Config, LogFormat},
+    error,
+    utils::error::Result,
+};
 
 /// Globally accessible metrics state
 pub(crate) static METRICS: Lazy<Metrics> = Lazy::new(Metrics::new);
@@ -119,8 +123,15 @@ pub(crate) fn init(config: &Config) -> Result<Guard, error::Observability> {
         .transpose()?
         .unzip();
 
-    let fmt_layer = tracing_subscriber::fmt::Layer::new()
-        .with_filter(EnvFilter::from(&config.log));
+    let fmt_layer =
+        tracing_subscriber::fmt::Layer::new().with_ansi(config.log_colors);
+    let fmt_layer = match config.log_format {
+        LogFormat::Pretty => fmt_layer.pretty().boxed(),
+        LogFormat::Full => fmt_layer.boxed(),
+        LogFormat::Compact => fmt_layer.compact().boxed(),
+        LogFormat::Json => fmt_layer.json().boxed(),
+    };
+    let fmt_layer = fmt_layer.with_filter(EnvFilter::from(&config.log));
 
     let subscriber = Registry::default()
         .with(jaeger_layer)