Environment Variable Configuration (#2)

## Problem

Some parameters should be definable via environment variables, but this
is not yet handled.

## Solution

Added support for providing API key, controller host, and additional
request headers through environment variables.

## Type of Change

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] This change requires a documentation update
- [ ] Infrastructure change (CI configs, etc)
- [ ] Non-code change (docs, etc)
- [ ] None of the above: (explain here)

## Test Plan

Test cases are written in `src/pinecone.rs`.

pinecone_sdk/Cargo.toml

@@ -8,5 +8,10 @@ edition = "2021"
 [dependencies]
 openapi = { path = "../openapi" }
 tokio = { version = "1", features = ["full"] }
-mockito = "0.30"
 regex = "1.10.4"
+serde_json = "1.0.117"
+snafu = "0.8.3"
+
+[dev-dependencies]
+mockito = "0.30"
+serial_test = "3.1.1"

pinecone_sdk/src/config.rs

@@ -1,7 +1,10 @@
+use std::collections::HashMap;
+
 #[derive(Debug, Clone)]
 pub struct Config {
     pub api_key: String,
     pub controller_url: String,
+    pub additional_headers: HashMap<String, String>,
     pub source_tag: Option<String>,
 }
 
@@ -10,6 +13,7 @@ impl Config {
         Config {
             api_key,
             controller_url: "https://api.pinecone.io".to_string(),
+            additional_headers: HashMap::new(),
             source_tag,
         }
     }

pinecone_sdk/src/control/list_indexes.rs

@@ -15,16 +15,14 @@ impl Pinecone {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use mockito::mock;
-    use tokio;
-    use crate::control::list_indexes::models::index_model::Metric;
     use crate::config::Config;
-    use openapi::models::IndexList;
-    use openapi::apis::configuration::Configuration;
+    use crate::control::list_indexes::models::index_model::Metric;
+    use mockito::mock;
     use openapi::apis::configuration::ApiKey;
+    use openapi::apis::configuration::Configuration;
+    use openapi::models::IndexList;
     use openapi::models::IndexModel;
-
-
+    use tokio;
 
     #[tokio::test]
     async fn test_list_indexes() {
@@ -66,7 +64,8 @@ mod tests {
 
         // Construct Pinecone instance with the mock server URL
         let api_key = "test_api_key".to_string();
-        let pinecone = Pinecone::new(api_key, Some(mockito::server_url()), None);
+        let pinecone = Pinecone::new(Some(api_key), Some(mockito::server_url()), None, None)
+            .expect("Failed to create Pinecone instance");
 
         // Call list_indexes and verify the result
         let result = pinecone.list_indexes().await;