feat(tags): Add tags on bills (WIP)

[almet]

Tags can now be added in the description of a bill, using a hashtag symbol (#tagname).

There is no way to "manage" the tags, for simplicity, they are part of the "what" field, and are parsed via a regular expression.

Statistics have been updated to include tags per month. Under the hood, a new tag table has been added.

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Todolist:

• [x] Add a new table and relationship
• [x] Parse the hashtags from the "what" field
• [x] Create the tags if they do not already exist
• [x] Display the tags in the bill list table
• [x] Compute the statistics for the tags as well
• [ ] write tests
• [ ] update the API

[almet]

A few remarks:

• I'm not even sure we should add a table for this. Maybe having an encoded list would be enough.
• I would need to expose this with the REST API
• Migrations would need to be run before adding these changes. It seems they haven't been created on latest mainbranch

[almet]

This now works properly. Tags are displayed on the main bill list, and monthly statistics have been updated.

Here are a few screen captures:

[Glandos]

My little experience on UI told me that we could have a little bit of CSS to show that it's a tag, e.g. using a rounded border and colored background. Like from Material design:

[zorun]

Nice work! I remember trying to convince you a few months ago that tags were more useful than simple categories, happy to see the result ;)

I haven't looked at the code, but I have a few questions UX-wise:

• what happens when there are lots of tags? Does it generate 100 columns in the statistics page?
• how does the list of bills look like on mobile with the new column? I remember it's quite tight already
• is this feature "discoverable", i.e. how can I know that I can enter tags in the "What" field?
• is there some auto-completion of tags to reuse existing ones, instead of creating slightly different tags? like #animal vs #Animal vs #animals

The statistics page is complex, we would like to show stats per month and per tag, but this is really a lot of data. Maybe something dynamic with javascript? I imagine showing just one amount per month, and then being able to click on tags to enable/disable them individually, and that would update the amount display per month.

Another nice visualisation for stats would be a breakdown: 20% of expenses for food, 10% for transport... Of course the total can be more than 100% if some bills have several tags, so I'm not sure how to present that meaningfully. We would need some user stories to guide the UX.