Admin KV editor must check for key existance before creating new key

[sisou]

Features:

• Database
• KV
• Blob
• Cache

Description:
I wanted to search for a key in the Hub Admin KV panel and accidentally put the key into the New key field (which is right above the search field!) and hit ENTER. And just like that, my key was overwritten with an empty object. No confirmation, no warning, no nothing. Production data lost.