[Cloudflare Logpush] Add content-type header to HTTP endpoint setup docs

[chemamartinez]

Proposed commit message

We have recently received feedback reporting that when configuring the HTTP endpoint for Cloudflare Logpush, incoming HTTP messages may contain an invalid Content-Type header while the HTTP endpoint input expects application/json. It leads to this error:

"error_message": "error 415: error pushing: error uploading to https: 415 {\"message\":\"wrong Content-Type header, expecting application/json\"}",

This pull request defines the Content-Type header when configuring the destination for the HTTP endpoint in the setup guide.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Related issues

• Closes Improve CloudFlare Logpush Documentation #8342

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[elasticmachine]

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• Start Time: 2023-11-13T09:06:34.840+0000

• Duration: 30 min 0 sec

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Test	Results
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Passed	115
Skipped	0
Total	115

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (18/18)	💚
Files	100.0% (18/18)	💚 3.86
Classes	100.0% (18/18)	💚 3.86
Methods	100.0% (215/215)	💚 7.804
Lines	91.959% (4883/5310)	👍 3.347
Conditionals	100.0% (0/0)	💚

[bhapas]

LGTM

[chemamartinez]

/test

[chemamartinez]

/test

[elasticmachine]

Package cloudflare_logpush - 1.17.1 containing this change is available at https://epr.elastic.co/search?package=cloudflare_logpush