RM-205: Add placeholder replacement for ticket messages and tags...

[biast12]

Description

RM-205
This PR does 3 thing

• Add placeholder replacement for ticket messages and tags
• Disable tag selector button in send message view when no tags are available
• fix a bug with tags not being able to be updated if they already had an option in it (Normalize empty embed fields to nil in tag creation)

Type of Change

• Bug fix
• New feature
• Breaking change
• Improvement

Testing

Make a tag both using content and an embed, add some placeholders into it, and try to send it via the dashboard, try to also use the placeholders to send messages via the dashboard too

Checklist

• My code follows the style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works