fix: loosen regex requirements for config keys

Signed-off-by: aramissennyeydd <aramis.sennyey@doordash.com>

packages/config-loader/src/sources/EnvConfigSource.ts

@@ -85,7 +85,7 @@ export class EnvConfigSource implements ConfigSource {
 const ENV_PREFIX = 'APP_CONFIG_';
 
 // Update the same pattern in config package if this is changed
-const CONFIG_KEY_PART_PATTERN = /^[a-z][a-z0-9]*(?:[-_][a-z][a-z0-9]*)*$/i;
+const CONFIG_KEY_PART_PATTERN = /^[\w-_]+$/i;
 
 /**
  * Read runtime configuration from the environment.

packages/config/src/reader.ts

@@ -18,7 +18,7 @@ import { JsonValue, JsonObject } from '@backstage/types';
 import { AppConfig, Config } from './types';
 
 // Update the same pattern in config-loader package if this is changed
-const CONFIG_KEY_PART_PATTERN = /^[a-z][a-z0-9]*(?:[-_][a-z][a-z0-9]*)*$/i;
+const CONFIG_KEY_PART_PATTERN = /^[\w-_]+$/i;
 
 function isObject(value: JsonValue | undefined): value is JsonObject {
   return typeof value === 'object' && value !== null && !Array.isArray(value);