fix: camelToSnake to respect uppercase words, such as "GetAPIValue" -…

…> "GET_API_VALUE" (#1046)

## Problem
`camelToSnake()` is converting the example string "TestAPI" ->
"TEST_AP_I" when converting a 3rd party integration proto files that I
am attempting to generate with the Nest option. I believe that the
conversion should respect the "API" part of the string and not split it
into two parts like so.

## Fix
I swapped the logic to use the already imported "case-anything"
library's `snakeCase()` function as `snakeCaseAnything()` and added a
couple of simple tests to ensure the logic.

I would love for this fix to go through as it is a pretty inconvenient
problem at the moment (:

Thanks!

src/case.ts

@@ -1,4 +1,4 @@
-import { camelCase as camelCaseAnything } from "case-anything";
+import { camelCase as camelCaseAnything, snakeCase as snakeCaseAnything } from "case-anything";
 
 import { Options } from "./options";
 
@@ -24,7 +24,7 @@ export function snakeToCamel(s: string): string {
 }
 
 export function camelToSnake(s: string): string {
-  return s.replace(/\w([A-Z])/g, (m) => m[0] + "_" + m[1]).toUpperCase();
+  return snakeCaseAnything(s).toUpperCase();
 }
 
 export function capitalize(s: string): string {

tests/case-test.ts

@@ -1,4 +1,4 @@
-import { maybeSnakeToCamel, camelCaseGrpc } from "../src/case";
+import { maybeSnakeToCamel, camelCaseGrpc, camelToSnake } from "../src/case";
 import { Options, optionsFromParameter } from "../src/options";
 import { getFieldJsonName } from "../src/utils";
 
@@ -51,6 +51,14 @@ describe("case", () => {
     expect(camelCaseGrpc("GetAPIValue")).toEqual("getApiValue");
   });
 
+  it("converts simple string to snake case, getApiValue === GET_API_VALUE", () => {
+    expect(camelToSnake("GetApiValue")).toEqual("GET_API_VALUE");
+  });
+
+  it("converts string to snake case respecting word separation, getAPIValue === GET_API_VALUE", () => {
+    expect(camelToSnake("getAPIValue")).toEqual("GET_API_VALUE");
+  });
+
   describe("getFieldJsonName", () => {
     it("keeps snake case when jsonName is probably not set", () => {
       expect(getFieldJsonName({ name: "foo_bar", jsonName: "fooBar" }, { snakeToCamel: [], useJsonName: false })).toBe(