*: refactor methods to support mocking

Additionally, write some tests to ensure the driver method
`startBlacksmithBuilder` handles all exceptions correctly in
both nofallback=true and nofallback=false configurations.

src/utils.ts

@@ -0,0 +1,59 @@
+import axios, {AxiosError, AxiosInstance, AxiosResponse} from 'axios';
+import * as core from '@actions/core';
+
+export async function getBlacksmithAgentClient(): Promise<AxiosInstance> {
+  const stickyDiskMgrUrl = 'http://192.168.127.1:5556';
+  return axios.create({
+    baseURL: stickyDiskMgrUrl
+  });
+}
+
+export async function postWithRetry(client: AxiosInstance, url: string, formData: FormData, retryCondition: (error: AxiosError) => boolean): Promise<AxiosResponse> {
+  const maxRetries = 5;
+  const retryDelay = 100;
+
+  for (let attempt = 1; attempt <= maxRetries; attempt++) {
+    try {
+      return await client.post(url, formData, {
+        headers: {
+          Authorization: `Bearer ${process.env.BLACKSMITH_STICKYDISK_TOKEN}`,
+          'X-Github-Repo-Name': process.env.GITHUB_REPO_NAME || '',
+          'Content-Type': 'multipart/form-data'
+        }
+      });
+    } catch (error) {
+      if (attempt === maxRetries || !retryCondition(error as AxiosError)) {
+        throw error;
+      }
+      core.warning(`Request failed, retrying (${attempt}/${maxRetries})...`);
+      await new Promise(resolve => setTimeout(resolve, retryDelay));
+    }
+  }
+  throw new Error('Max retries reached');
+}
+
+export async function postWithRetryToBlacksmithAPI(url: string, requestBody: unknown, retryCondition: (error: AxiosError) => boolean): Promise<AxiosResponse> {
+  const maxRetries = 5;
+  const retryDelay = 100;
+  const apiUrl = process.env.BLACKSMITH_ENV?.includes('staging') ? 'https://stagingapi.blacksmith.sh' : 'https://api.blacksmith.sh';
+
+  for (let attempt = 1; attempt <= maxRetries; attempt++) {
+    try {
+      const fullUrl = `${apiUrl}${url}`;
+      return await axios.post(fullUrl, requestBody, {
+        headers: {
+          Authorization: `Bearer ${process.env.BLACKSMITH_STICKYDISK_TOKEN}`,
+          'X-Github-Repo-Name': process.env.GITHUB_REPO_NAME || '',
+          'Content-Type': 'application/json'
+        }
+      });
+    } catch (error) {
+      if (attempt === maxRetries || !retryCondition(error as AxiosError)) {
+        throw error;
+      }
+      core.warning(`Request failed, retrying (${attempt}/${maxRetries})...`);
+      await new Promise(resolve => setTimeout(resolve, retryDelay));
+    }
+  }
+  throw new Error('Max retries reached');
+}