feat: add support for custom environment variable expansion

.changeset/feat_env_var_expansion.md

@@ -0,0 +1,15 @@
+### feat: add support for custom environment variable expansion - @gocamille PR #539
+
+#### Summary
+
+This PR adds support for `${env.VAR_NAME}` syntax in configuration files, allowing users to reference custom environment variables without being limited to the `APOLLO_MCP_*` naming convention.
+
+Closes #454.
+
+#### Changes
+
+- `runtime/env_expansion.rs` (new module) - parser for variable expansion
+- `runtime.rs` (modified) - integrates expansion into the `read_config()` function
+- `config-file.mdx` - updated docs with syntax, escaping, and special characters handling
+
+- **Note** The `APOLLO_MCP_*` environment variable(s) will still take precedence over expanded custom config values (no breaking change).

crates/apollo-mcp-server/Cargo.toml

@@ -56,6 +56,8 @@ rmcp = { version = "0.9", features = [
 schemars = { version = "1.0.1", features = ["url2"] }
 serde.workspace = true
 serde_json.workspace = true
+serde_yaml = "0.9.34"
+shellexpand = { version = "3.1", default-features = false, features = ["base-0"] }
 thiserror.workspace = true
 tokio.workspace = true
 tokio-util = "0.7.15"