Replace Fastly VCL cstr_escape w/ json.escape

[akesle]

Purpose of this pull request

Bring Sumo Logic's Fastly integration VCL examples in line with Fastly's own documentation for integrating with Sumo Logic. This concerns the preferred use of the VCL json.escape function over the somewhat ineffective (in the context of JSON) use of the suggested cstr_escape.

TL:DR Using cstr_escape in a Fastly VCL log format string may still result in invalid JSON sequences, whereas substituting json.escape will alleviate all those issues.

Select the type of change

• Minor Changes - Typos, formatting, slight revisions
• Update Content - Revisions, updating sections
• New Content - New features, sections, pages, tutorials
• Site and Tools - .clabot, version updates, maintenance, dependencies, new packages for the site (Docusaurus, Gatsby, React, etc.)

Ticket (if applicable)

Originated by Fastly.

[cla-bot]

Thank you for your contribution! As this is an open source project, we require contributors to sign our Contributor License Agreement and do not have yours on file. To proceed with your PR, please sign your name here and we will add you to our approved list of contributors.

[kimsauce]

Hi @akesle,

Thank you for your contribution to the Sumo Logic Fastly documentation! We truly appreciate your time and effort in improving our docs—it means a lot coming from a Fastly engineer.

Before we can merge your changes, we kindly ask you to sign our Contributor License Agreement (CLA). Once you've signed it, let us know, and we'll proceed with reviewing and merging your contribution.

Thanks again for your help! Let us know if you have any questions.

Best,
Kim
Sumo Logic Documentation Team

[jpipkin1]

@akesle, I noticed that your PR submits changes directly to the main branch. Please place your changes in a new branch to protect main from unforeseen issues that could arise (see our contribution guide).

[akesle]

@akesle, I noticed that your PR submits changes directly to the main branch. Please place your changes in a new branch to protect main from unforeseen issues that could arise (see our contribution guide).

Thank you for the documentation reference. I will close this PR and re-open from a designated branch.