discord message size fixes

[piksel]

solves two panic conditions when using the discord service:

• sending an empty message without a title
  (fixes Sending zero characters to discord panics with index out of range error #239)
• sending a message with partitioning and a message that is a modulus of the configured chunk size
  (fixes Sending 2000, 4000 or 6000 characters to Discord panics in util.PartitionMessage (index out of range) #240)

[codecov]

Codecov Report

Merging #242 (ba99f9e) into main (6dbcb12) will increase coverage by 0.55%.
The diff coverage is 100.00%.

❗ Current head ba99f9e differs from pull request most recent head 616f2c6. Consider uploading reports for the commit 616f2c6 to get more accurate results

@@            Coverage Diff             @@
##             main     #242      +/-   ##
==========================================
+ Coverage   77.07%   77.63%   +0.55%     
==========================================
  Files          95       95              
  Lines        2844     2857      +13     
==========================================
+ Hits         2192     2218      +26     
+ Misses        473      466       -7     
+ Partials      179      173       -6     

Impacted Files	Coverage Δ
pkg/services/discord/discord.go	81.25% <100.00%> (+24.72%)	⬆️
pkg/services/discord/discord_json.go	92.59% <100.00%> (+0.92%)	⬆️
pkg/util/partition_message.go	95.74% <100.00%> (+0.29%)	⬆️
pkg/services/slack/slack_json.go	100.00% <0.00%> (ø)
pkg/services/discord/discord_config.go	88.23% <0.00%> (+5.88%)	⬆️

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[piksel]

@all-contributors add @justinsteven for bug

[allcontributors]

@piksel

I've put up a pull request to add @justinsteven! 🎉